I keep seeing posts on the newsgroups saying the people are having problems with Visual SourceSafe and aspx pages. The problem occurs when the user tries to open the file in Visual Studio. When this happens the user is prompted to check the file out even when they are not trying to edit it.
This is not actually a problem with SourceSafe, the same thing would occur with any source control program. The real problem is that Visual Studio is trying to modify the file. It does this when opening the file in design view. There are a number of reasons why it does this, none of which seem to make sense. The one I have come across is that if you set the tag to be run at server the designer tries to change it back
The work around I have is to open the file in HTML view and edit the HTML directly and not use the designer. To set the HTML view as default you need to select the Tools/Options menu item. This brings up the options dialog. In the tree view at the left select HTML Designer/General. Finally select HTML View for each of the three options on the right.
I know this is not an ideal solution but it is the best you are going to get at the moment.