The new talk of the SEO world is ‘Canonical URL‘. What is canonical URL? This is the definition given in Google’s Webmaster Central Blog…

a format that allows you to publicly specify your preferred version of a URL. If your site has identical or vastly similar content that’s accessible through multiple URLs, this format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version.

Emphasis mine

It is very easy to specify the canonical URL of a page – all you have to do is add this line in the head section…

<link rel="canonical" href="http://binnyva.com/" />

The purpose of this tag is to prevent the problem of duplicate content.

The best thing about this tag is that all three major search engines(Google, Yahoo and MS Live) support this initiative.

WordPress

If you are on wordpress, this tag can be integrated into your theme easily. There is a plugin to do the job for you – but you don’t need a plugin to do something as simple as this.

header.php

Go to the theme folder in wordpress(wp-content/themes/<theme_name>) and open the file header.php in your favorite editor. Now find the line…

</head>

and add the following code before that line…

<?php if ( is_singular() ) { ?>
<link rel="canonical" href="<?php the_permalink(); ?>" />
<?php } ?>

Now, it should look something like this…

<?php if ( is_singular() ) { ?>
<link rel="canonical" href="<?php the_permalink(); ?>" />
<?php } ?>
</head>

That’s it – you are done! Save the file and upload it to your server.

This fix will add the canonical URL tag to all the posts and pages of your blog. If you want to see a blog that have implemented this fix, take a look at the source of this page.

Related Links

• Canonical URL
• What Is A Canonical URL?
• Canonical URLs To Avoid Duplicate Content
• Learn about the Canonical Link Element in 5 minutes

I just released my first firefox plugin – URL Lister. It shows the URLs of all the open tabs in a textarea so that they can be copied easily.

Download/Install

Install URL Lister

If you have installed it, consider rating it or reviewing it at Firefox plugins sandbox. Go to the public page for URL Lister and write a review for the application. I need reviews to promote it to the main extensions page – sandbox plugins are for registered users only.

Usage

Lets say you have these four tabs open…

• OpenJS – JavaScript, Opened.
• Bin-Co
• LinDesk
• BinnyVA

Right click any tab and click on the ‘URL Lister…’ to open up the main dialog. You can also use ‘Tools > URL Lister’. You will find the URLs of all the open tabs there.

There is a drop down menu at the bottom – it has these three options…

• Plain Text
• HTML Anchors
• Linked List

Open URLs

If you have a list of URLs and want to open them all, all you have to do is copy those URLs into this dialog and press OK – this will open up all the given URLs.

And my thanks goes to…

URL Lister is sort of a response to this post by Matt Cutts. I want to thank him for the idea.

There is another plugin with a similar function – Tab URL Copier. I lifted some code from that plugin when creating URL Lister. Thanks.

Are URLs Case Sensitive?

They should not be – but they sometimes are. Domain names are not case sensitive – for example http://www.apache.org/ and http://WWW.Apache.Org/ goes to the same location. But in the LAMP platform, the path is case sensitive…

• http://www.apache.org/foundation/getinvolved.html is not
• http://www.apache.org/Foundation/GetInvolved.HTML

But in the case of Microsoft IIS server, this is not true – try…

• http://www.microsoft.com/WindowsServer2003/IIS/Default.mspx is the same as
• http://www.microsoft.com/windowsserver2003/iis/default.mspx

Reason: Linux Filesystem is Case Sensitive

The root cause of this is that the filesystem in the Linux OS is case sensitive – while FAT32/NTFS filesystems in Windows are not.

Dynamic URLs

Now Dynamic/friendly/clean URLs are appearing in many CMS tools. A good example for this is the ‘permalink structure’ in WordPress. These dynamic URLs could be case sensitive or not – it depends on the software. In WordPress they are case insensitive. Del.icio.us is also case insensitive. TinyURL is another service that uses case insensitive URLs. But it is possible for the tool to make the URLs case sensitive.

From the SEO perspective

If the search bot visits two urls say, example.com/MyWebPage/Index and example.com/mywebpage/index , will the bot index both page contents? If they are same, will one get the duplicate content penalty? Or will google just index the URL with lower case and ignore the other – remember, in Linux/Apache, both pages may have different content.

Conclusion

The RFC for URL says they must be case insensitive.

For resiliency, programs interpreting URLs should treat upper case letters as equivalent to lower case in scheme names (e.g., allow “HTTP” as well as “http”).

Apache must not use the filesystem as an excuse – I really hope they provide case insensitive URLs