URL Rewrite with SharePoint 2007/2010/2013

Redirection is the use of HTTP status codes 301 or 302 to redirect the client to a different location, which involves an additional client round trip.

Rewriting is actually changing both incoming and/or outgoing URLs. Any implementation of such rewrites is unsupported with SharePoint unless the path is symmetrical.

For example, you can modify the path of a request, such as http://www.contoso.com/sharepoint/default.aspx, which is forwarded to the SharePoint server as http://sharepoint.perimeter.example.com/default.aspx. This is referred to as an asymmetrical path.

SharePoint Server 2007/2010/2013 do NOT support asymmetrical paths. The path of the URL must be symmetrical between the public URL and the internal URL. In the above example, this means that the /SharePoint/default.aspx portion of the URL must not be modified by any external tool.

For More Information :
http://support.microsoft.com/kb/2818415