In this article of the SEO (search engine optimisation) manual I will be talking about the ISAPI Rewrite server module. When working on SEO for a website been able to rewrite the URL the user enters is vital. Doing this allows us to make page links much more search engine friendly. For example if you were to go to most online shops you will notice that they have URLs like http://www.myshop.com/Cat1/Cat2/Product5.html. What your looking at normally is a rewritten URL, this means the web server is processing the page http://www.myshop.com/products.php?product=5&cat=Cat1&subcat=Cat2. Though most UNIX web servers use Apaches mod_rewrite module, Microsoft servers cannot use this same module as it is incompatible. This is where ISAPI Rewrite comes in.
ISAPI Rewrite works in very much the same way as mod_rewrite, they both use files placed in directories to get their configuration. Using mod_rewrite you would create a file named “.htaccess” whereas with ISAPI Rewrite you would name the file “httpd.ini”. Both server modules allow the use of Regular Expressions when rewriting URLs. This is very handy when it comes to sites like the example I mentioned above. Using Regular Expressions you do not need to enter every variation of the URL, you can use something similar to
RewriteRule (.*)/(.*)/Product(.*).html /products.php?product=$3&cat=$1&subcat=$2

What this is telling the server is that anything that the user enters that contains 2 variables separated by slashes then matching the Product and the .html each part that says (.*) is telling the server that this portion of the string can be anything and it should be stored in a variable, on the actual URL (products.php?…) each $ represents where the variable for each portion should go. This makes the rewriting of URLs very easy when you are dealing with, in theory, unlimited products and categories. There is a huge amount of information available for both modules ISAPI Rewrite and mod_rewrite, both from the companies who make the modules and many third party websites around the web.

I hope this article is found to be useful and interesting and encourages you to take the plunge and make your website more search engine friendly, whether it be through content or your links.

In earlier articles, we have explained the importance of rewriting your URLs in order to benefit your Search Engine Optimisation (SEO). BUT BE WARNED, if your existing URLs have alot of pre-existing links going to them, then rewriting the URL will damage your ranking, as the links going to the URL which is getting rewritten will lose around 10% of their value in the rewrite. This can be very damaging in the short term, but possibly very advantageous in the long term, this has to be weighed up on a case by case basis. An example of when you should use a rewritten URL is as follows: Lets say that you ran a mobile phone site www.mobilephone.com and you had a page about a specific product, lets say a ‘HTC-Diamond’ phone. Your URL should look something like this:

www.phone.com/htc-diamond

and not the standard

www.phone.com/index.php?main_page=index&cPath=6_254#

There are a number of ways to achieve this, and alot depends on what server side language that your site uses. For the majority of e-commerce sites out there, currently PHP is the sever side language of choice, the other main one is ASP.net. The reason PHP is the most popular is all down to three reasons; firstly, it open sources no hefty price tag, secondly, PHP is much more complex in its coding but is easier to tailor than ASP and finally, its Mod Rewrite capability through use of a .htaccess file on a per-directory basis. Incorrect use of a .htaccess file can bring your site down in a flash, so be careful when doing mod rewrites and always have a backup standing by of your last good .htaccess configuration. .htaccess can easily be written in notepad and for mod rewrites, there should always be the first line “RewriteEngine on”, this turns on the rewrite capability of the .htaccess. There are a large number of things that you can do with the .htaccess file once it is turned on, there are too many to go into in this blog, but I would recommend that you search the web for .htaccess cheat sheets. To learn more on this topic, here is a good page which will get you started.