Hi Avonelle Lovhaug,
In order to perform rewriting of htm/html pages, you should map these extensions to the ASP.NET ISAPI. If you do not do it, the request will not reach Asp.Net and Sitefinity at all, so the URL Rewriter will not be even aware that a request has been made.
If you are running IIS7 in integrated pipe line mode, then you have wildcard mapping turned on (all request are going for Asp.Net processing).
Once you have the mapping (or the wildcard mapping), add the highlighted to the web.config file:
In this case Sitefinity will be aware that the htm/html requests should be processed.
I hope this helps.
the Telerik team