If you are building a new ASP.NET application, SEO has become a big factor in how you plan the structure / code of the site.  But quite an important part of the site which are often overlooked are the URL’s, and a lot of people do the basics which I’ll show below but there are a few common things people tend to miss or never thought could be a problem. I use ISAPI rewrite for most of my sites, which is an amazingly effective tool for sorting duplicate content and SEO issues which I’ll show below

1.) Rewrite your URL’s to be useful / descriptive and stick away from using the old dynamic way

i.e. mypage.aspx?e=54&b=99

Google even tell you this is not ideal in the webmaster guidelines (See bottom of Design & Content Guidelines section) - http://www.google.co.uk/support/webmasters/bin/answer.py?answer=35769&hlrm=en_uk

2.) Strip our non alpha numeric characters from the URL and use Hyphens to separate words

Regex.Replace(strInput, "[^\w]", "-")

3.) Replace & (Ampersands) in URLS with the word ‘and’ so a page called ‘Microsoft & Google’ might have a URL like

microsoft-and-google.htm

I use this function to rewrite my URL’s

    Function CreateURLs(ByVal strInput As String) As String
        strInput = strInput.Replace("&", "and")
        strInput = Regex.Replace(strInput, "[^\w]", "-")
        strInput = strInput.Replace("----", "-")
        strInput = strInput.Replace("---", "-")
        strInput = strInput.Replace("--", "-")
        If strInput.EndsWith("-") Then
            strInput = strInput.Substring(0, strInput.Length - 1)
        End If
        strInput = LCase(strInput)
        Return strInput
    End Function

4.) Try to keep away from using URL’s that have multiple folders, as it

/Home/Something/this/that/12/

If you have to have your URL’s like this then at least make them as short as possible, descriptive and stick away from numeric's like

/Cat14/SubCat77/521

Try to use URL’s that makes sense, the new Whitehouse site is a good example of how to use this type of URL rewriting effectively

http://www.whitehouse.gov/about/presidents/johnfkennedy/

5.) Turn your pages into .htm/.html extensions instead of .aspx with ISAPI Rewrite – This little trick just tells ISAPI to treat .htm files as .aspx files.

RewriteEngine on
RewriteRule ^(.*)\.htm $1\.aspx

There is no written evidence that changing your extension to .htm from .aspx will help your SEO – But personally from running a few successful stores and sites, the sites with the .htm extensions pages just ‘seem’ to do a lot better in the SERPS.

TIP!: In case you need to have a folder that doesn’t treat .htm files as .aspx you can add this to ISAPI (The middle line)

RewriteEngine on
RewriteRule  ^FolderToIgnore/  -  [L]
RewriteRule ^(.*)\.htm $1\.aspx

Tip of the hat to iamlost on cre8asite for this gem

6.) Keep your URL’s lowercase and 301 redirect any non lowercase URL’s (using ISAPI rewrite)

RewriteEngine on
RewriteMap  lc int:tolower
RewriteCond %{REQUEST_URI} [A-Z]
RewriteRule (.*) ${lc:$1} [R=301,L]
RewriteRule ^(.*)\.htm $1\.aspx 

This is to stop duplicate content and if anyone has linked to you via an uppercase URL, as still the search engines seem to be treating the same page with different case letters as two different pages – So Default.htm & default.htm can be seen as separate pages! Crazy… I know…!

7.) And a free seventh tip… Well its not really an SEO / URL related tip, but get yourself signed up and site registered with the Google Webmaster Tools