Tìm Hiểu về Wordpress - part 31 pps

Returning to our movie example for a moment, our WordPress-powered site may suffer in the search rankings because identical copies of our movie article are appearing at each of the follo

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8.1.1 SEO Strengths and Weaknesses

Out of the box, WordPress provides great flexibility in terms of organizing and

managing your blog’s content Much of this flexibility comes by way of WordPress’

category and tag architecture Each and every post created on your blog may be

assigned to any number of both categories and tags

Categories are meant to classify content according to broad definitions, while

tags are used to classify content more specifically For example, a post about your

favorite movies may be categorized in the “Favorite Movies” category, while being

tagged for some of the movies featured in the article: “Star Wars,” “The Matrix,”

and “Blade Runner.”

Beyond this central organizing principle, WordPress brings with it many strengths

and weaknesses in terms of how content is organized and made available to both

users and the search engines Let’s examine some of these SEO factors before

digging into the fine art of optimizing your WordPress-powered site for the

search engines

8.1.2 Strong Focus on Content

Content, as they say, is king The Web exists because of it Users are searching for

it Search engines are built on it In order to succeed on the Web, your site should

be focused on delivering useful content above all else Awesomely, one of the main

goals of WordPress is to make publishing content as easy as possible

Search Engine Optimization

8

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Once WordPress is set up, getting your content online happens as fast as you can create it On the front end, there are hundreds of top-quality themes available, each focused on organizing and presenting your content with both users and search engines in mind

8.1.3 Built-In “nofollow” Comment Links

Perhaps not as useful as originally conceived, nofollow attributes placed on commentator links have long been thought of as an effective method of improving the SEO-quality of WordPress-powered sites For those of you who may be

unfamiliar with the whole “nofollow” thing, for now suffice it to say that nofollow attributes are placed on links to prevent search engines from following those links

to their targets Originally, this was intended to serve as a way to conserve valuable page rank, but after it was revealed that this method no longer works, nofollow commentator links may be a moot point We’ll discuss this more in-depth later on

in the chapter

8.1.4 Duplicate Content Issues

While the organizational strengths of WordPress are great for managing content, it also comes with a price: duplicate content Duplicate content is essentially identical content appearing in more than one place on the Web Search engines such as Google are reported to penalize pages or sites associated with too much duplicate content Returning to our movie example for a moment, our WordPress-powered site may suffer in the search rankings because identical copies of our movie article are appearing at each of the following URLs:

• original article -> http://example.com/blog/my-favorite-movies/

• category view -> http://example.com/blog/category/favorite-movies/

• star-wars tag view -> http://example.com/blog/tag/star-wars/

• the-matrix tag view -> http://example.com/blog/tag/the-matrix/

• blade-runner tag view -> http://example.com/blog/tag/blade-runner/

WordPress + nofollow

Check out Chapter 7.7.3 for

more information on nofollow,

WordPress, and the search

engines.

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Yikes! And if that weren’t bad enough, we also see the exact same post content

appearing at these URLs:

• daily archive view -> http://example.com/blog/2009/02/02/

• monthly archive view -> http://example.com/blog/2009/02/

• yearly archive view -> http://example.com/blog/2009/

• author archive view -> http://example.com/blog/author/your-name/

Depending on your particular WordPress theme, this situation could be even worse

By default, all of your posts are available in identical form at each of the previous

types of URLs Definitely not good from a search-engine point of view Especially if

you are the type of blogger to make heavy use of tags, the number of duplicated

posts could be staggering

8.2.1 Controlling Duplicate Content

Fortunately, WordPress’ poor handling of duplicate content is easily fixed In fact,

there are several ways of doing so In a nutshell, we have plenty of tools and

techniques at our disposal for winning the war on duplicate content:

• meta nofollow tags

• meta noindex tags

• nofollow attributes

• robots directives

• canonical meta tags

• use excerpts for posts

So what do each of these sculpting tools accomplish and how do they help us

eliminate duplicate content? Let’s take a look at each of them

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8.2.2 Meta noindex and nofollow Tags

Meta nofollow tags are actually inline link elements located in the <head> section

of your WordPress pages For example, in your blog’s “header.php” file, you may find something like this:

This code tells search engines – specifically, Google, MSN/Bing, and any other compliant search engine – that the entire page should be indexed, followed, and archived This is great for single post pages (i.e., the actual “My Favorite Movies” article posted in our example), but we can use different parameters within these

elements to tell the search engines not to index, follow, or archive our web pages.

Ideally, most bloggers want their main article to appear in the search results The duplicate content appearing on the other types of pages may be controlled with this set of meta tags:

Here, we are telling the search engines not to include the page in the search

engine results, while at the same time, we are telling them that it is okay to crawl the page and follow the links included on the page This prevents the page from appearing as duplicate content while allowing link equity to be distributed throughout the linked pages Incidentally, we may also tell the search engines to neither index nor follow anything on the page by changing our code to this:

Love Juice

Anyone dipping into the murky

waters of SEO will inevitably

discover that there are many

ways to refer to the SEO value

of web pages PR, Page rank,

link equity, link juice, page

juice, link love, love juice, rank

juice, and just about any other

combination of these terms

is known to refer to the same

thing: the success of a web

page in the search engines.

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So, given these meta tags, what is the best way to use this method to control

duplicate content on your WordPress-powered site? We’re glad you asked By using

a strategic set of conditional tags in the “header.php” file for your theme, it is

possible to address search-engine behavior for virtually all types of pages, thereby

enabling you to fine-tune the indexing and crawling of your site’s content To see

how this is done, consider the following code:

<?php if(is_home() && (!$paged || $paged == 1) || is_single()) { ?>

<?php } else { ?>

<?php } ?>

Tell Search Engines not to Index a Specific Post

In this section we see how to disable search-engine indexing for different categories, archives, pages, and other page views, but what if we want to prevent indexing of only one specific post? There are several SEO plugins that enable this functionality, but you don't really need one to do it All you need to do is get the ID of the post for which you would like to disable indexing Then, open your theme’s header.php file and place this snippet within the <head> section:

<?php if ($post->ID == 77) { echo '<meta name="robots" content="noindex,noarchive">'; }

Change the ID from “ 77 ” to the ID of your post and done! With this in place, compliant search engines such as Google and MSN/ Bing will neither index nor archive the specified post (ID #77 in this example).

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The conditional PHP tags used in this example effectively are saying: “If the current page is the home page or the single post page, then allow the search engines to both index and follow the content of the page; otherwise, since the page is neither the home page nor the single post page, it is probably a tag page, category page,

or other archive page and thus serves as duplicate content; therefore tell the search engines to follow all links but not index the content.”

Of course, it isn’t always a bad thing to have some peripheral pages indexed in the

search engines In addition to having their home page and single pages indexed (as

in our example above), many people prefer to have either tag pages or category pages (or both!) indexed in the search engines as well In reality, the types of pages that you want indexed are completely up to you and your personal SEO strategy

Prevent Duplicate Content Caused

by Paginated Comments

Since WordPress 2.7, comments may be paginated, such that “x” number of comments appear on each page While this is a step in the right direction, there may be a duplicate content issue resulting from the fact that

your post content will appear on every page of your paginated comments To resolve this issue, place the

following code into your functions.php file:

// prevent duplicate content for comments

function noDuplicateContentforComments() {

global $cpage, $post;

if($cpage > 1) {

echo "\n".'<link rel="canonical" href="'.get_permalink($post->ID).'" />'."\n";

}

add_action('wp_head', 'noDuplicateContentforComments');

This code will generate canonical <head> links for your all of your paginated comments The search engines will then use this information to ensure that the original post permalink is attributed as the actual article

Further Information

For more information and techniques on paged comments and duplicate content, check out Chapter 7.3.3.

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So, if you would like to include both tag and category pages

in the search results, you would simply modify the first line

of our previous example like so:

<?php if(is_home() && (!$paged || $paged == 1) || is_

category() || is_tag() || is_single()) { ?>

8.2.3 Nofollow Attributes

Another useful tool in the fight against duplicate WordPress

content is the controversial “nofollow” attribute The

nofollow attribute is placed into hyperlinks like this:

<a href="http://domain.tld/path/target/"

rel="nofollow">This is a "nofollow" hyperlink</a>

Links containing the nofollow attribute will not be

“followed” by Google, but may still be indexed in the search

results if linked to from another source Because such links

are not followed, use of the nofollow attribute is an effective

tool in the reduction and prevention of duplicate content

For an example of how nofollow can be used to help

eliminate duplicate content, let’s look at a typical author

archive In the author-archive page view, you will find

exact replicas of your original posts (unless you are using

excerpts) This duplicate content is highly avoidable by

simply “nofollowing” any links in your theme that point to

the author-archive page view Here is how the nofollow link

would appear in your theme files:

<a href="http://domain.tld/author/author-name/"

rel="nofollow">This link will not be followed to the

author archive</a>

Exclude Admin Pages from Search Engines

You may also replace or add other types

of pages to your meta-tag strategy by using any of the following template tags:

• is_home() • is_page()

• is_admin() • is_author()

• is_date() • is_search()

• is_404() • is_paged()

• is_category() • is_tag()

• is_date()

To target any date-based archive page (i.e a monthly, yearly, daily or time-based archive) that is being displayed, use this:

• is_archive() Remember, there are more than just date-based Archives Other types of Archive pages include sequential displays

of category, tag, and author pages

is_archive() will target all of these page types

And of course there are many more types

of these conditional tags available to WordPress See the WordPress Codex for more information: http://digwp.com/u/3

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Ever wanted to keep a few specific pages out of the

search engines? Here's how to do it using WordPress’

excellent conditional tag functionality

Just place your choice of these snippets into the <head>

section of your header.php file and all compliant search

engines (e.g., Google, MSN/Bing, Yahoo!, et al) will

avoid the specified page(s) like the plague

This menu of snippets provides many specific-case

scenarios that may be easily modified to suit your needs

Exclude a specific post

<?php if(is_single('17')) { // your post ID number ?>

<?php } ?>

Exclude a specific page

<?php if(is_page('17')) { // your page ID number ?>

<?php } ?>

Exclude a specific category

<?php if(is_category('17')) { // your category ID number ?> <meta name="googlebot" content="noindex,noarchive,follow" /> <meta name="robots" content="noindex,follow" />

<?php } ?>

Exclude a specific tag

<?php if(is_tag('personal')) { // your tag name ?>

<?php } ?>

Exclude multiple tags

<?php if(is_tag(array('personal','family','photos'))) { ?> <meta name="googlebot" content="noindex,noarchive,follow" /> <meta name="robots" content="noindex,follow" />

<?php } ?>

Exclude posts tagged with certain tag(s)

<?php if(has_tag(array('personal','family','photos'))) { ?> <meta name="googlebot" content="noindex,noarchive,follow" /> <meta name="robots" content="noindex,follow" />

<?php } ?>

Exclude Specific Pages from Search Engines

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Granted, using nofollow links to control duplicate content is not 100% foolproof

If the author-archive URL is linked to from any “followed” links, that page still

may be indexed in the search engines For pages such as the author archives

that probably aren’t linked to from anywhere else, nofollow may help prevent a

potential duplicate-content issue

8.2.4 Robots.txt Directives

Another useful and often overlooked method of controlling duplicate content

involves the implementation of a robots.txt file for your site Robots.txt files are

plain text files generally placed within the root directory of your domain

http://domain.tld/robots.txt

Robots.txt files contain individual lines of well-established “robots” directives

that serve to control the crawling and indexing of various directories and pages

Search engines such as Google and MSN that “obey” robots directives periodically

read the robots.txt file before crawling your site During the subsequent crawl of

your site, any URLs forbidden in the robots.txt file will not be crawled or indexed

Keep in mind, however, that pages prohibited via robots directives continue to

consume page rank So, duplicate content pages removed via robots.txt may still

be devaluing your key pages by accepting any link equity that is passed via

incoming links

Even so, with other measures in place, taking advantage of robots.txt directives is

an excellent way to provide another layer of protection against duplicate content

and unwanted indexing by the search engines

Let’s look at an example of how to make a useful robots.txt file First, review the

default directory structure of a WordPress installation in the screenshot (next page)

For a typical WordPress installation located in the root directory, there is no reason

for search engines to index URLs containing any of the core WordPress files So we

begin our robots.txt file by writing:

Yahoo! Disobeys

Sadly, when it comes to search engines that comply with robots.txt directives, Yahoo! falls far short:

http://digwp.com/u/218

Not Foolproof

Pages blocked by robots.txt directives may still appear within the index if linked to by

“trusted, third-party sources.”

http://digwp.com/u/219

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Disallow: /wp-*

Disallow: *.php

These two lines tell compliant search engines to ignore any URL beginning with

“http://domain.tld/wp-” or ending with “.php” Thus, all of our core WordPress files are restricted and will not be crawled by compliant search engines

Now, consider some of the types of WordPress-generated URLs that we don’t want the search engines to follow or index:

http://domain.tld/feed/ - your site's main feed http://domain.tld/comments/feed/ - your site's comments feed http://domain.tld/other/feeds/ - every other type of feed http://domain.tld/post/trackback/ - every trackback URL on your site http://domain.tld/2008/08/08/ - archive views for every day http://domain.tld/2008/08/ - archive views for every month http://domain.tld/2008/ - archive views for every year

Of course, there are other types of pages which we may also wish to exclude from the search engines, such as category and tag archives, but you get the idea

To prohibit robots-compliant search engines from accessing and indexing the miscellaneous pages listed above, we add these directives to our robots.txt file: Disallow: */feed*

Disallow: */trackback*

Disallow: /20*

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