This is fairly undocumented piece of information which I have got from this blog
I havn't tried it myself, so I cannot gaurantee its completeness. I am posting it
here for the sake of interest and community .....
In the web.config file in the Sharepoint virtual directory contains the following section:
<Sharepoint><SafeMode MaxControls="200" CallStack="false" DirectFileDependencies="10" TotalFileDependencies="50" AllowPageLevelTrace="false"><PageParserPaths></PageParserPaths></SafeMode>:</Sharepoint>
By default the node <PageParserPaths> is empty. You can add <PageParserPath> nodes to specify the
virtual paths where you want to allow server side scripts:
<PageParserPaths><PageParserPath VirtualPath="/pages/*" CompilationMode="Always" AllowServerSideScript="true" IncludeSubFolders="true"/></PageParserPaths>
Where CompilationMode is one of the following values:
The page should always be compiled (default value)
ASP.NET will not compile the page, if possible.
The page or control should never be dynamically compiled.
I assume that the AllowServerSideScript and IncludeSubFolders flags speak for themselves.
careful with the virtual paths you specify in your PageParserPaths.
Anyone that can modify or add a page to the virtual path can insert
code that will be executed server side with no restrictions.
good location to specify as a PageParserPath is the location where you
store your masterpages, for example /_catalogs/masterpage. You can now
add server side script to your masterpages, which makes it available in
all pages using this masterpage.