We were having trouble adding a user to a site collection.  Every time we hit the search button or clicked the check userid button the system would just sit there and spin. I added the following section of the web.config to resolve the issue. </compilation> <pages enableSessionState="false" enableViewState="true" enableViewStateMac="true" validateRequest="false" pageParserFilterType="Microsoft.SharePoint.ApplicationRuntime.SPPageParserFilter, Microsoft.SharePoint, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" [...]

There are several steps that you need to take in order to enable anonymous access.  Below are the steps taken from Microsoft TechNet. Enable anonymous access for a zone of a Web application From Administrative Tools, open the SharePoint Central Administration Web site application. On the Central Administration home page, click Application Management. On the [...]