Do you have multiple entrances to your site and looking for a client-side solution that can redirect your visitors to the preferred entrance?
For example, you may have multiple domain names pointing to the same site -- domain_a.com, domain_b.com and domain_c.com. Although you want to keep all of your domains either because you want to reserve those names, because your marketing department convinced you that having multiple names pointing to the same site will attract more visitors or some other reason, you may prefer that the visitors end up at the same domain. You may want to redirect visitors from domain_b.com and domain_c.com to domain_a.com for example.
Following is a client-side solution to redirecting visitors to your preferred domain. Simply copy and paste it on to your home page just below the tag.

<script type="text/javascript" language="JavaScript">
<!-- Advertisement

if( -1 == location.href.
toLowerCase().
indexOf('domain_a.com') )
{
location.href = 'http://domain_a.com';
}
// -->
</script>

Above code will check if domain_a.com is a part of the current URL. If not, it will automatically redirect the visitor to http://domain_a.com. One of the advantages is that this code will work even if you have a single version of your home page that has multiple domain names pointing to it.
Of course you can modify the same code to redirect to a specific page URL as well.
Be sure to use only the required portion of your URL and to enter it in lowercase inside the function "indexOf()". If your complete URL is http://www.mycompany.com/mypage.html, but you can get to the same page using just mycompany.com/mypage.html, use the latter version of the URL. On the other hand, use the full URL for location.href.

The following code will redirect visitors to http://www.mycompany.com/mypage.html only if mycompany.com/mypage.html is not a part of the URL they typed:

<script type="text/javascript" language="JavaScript">
<!--
if( -1 == location.href.
toLowerCase().
indexOf('mycompany.com/mypage.html') )
{
location.href =
'http://www.mycompany.com/mypage.html';
}
// -->
</script>