By default, web.config of SharePoint (should be there: C:\Inetpub\wwwroot\wss\VirtualDirectories\80) defines the maximum number of controls as 200. Should you define more on a page you’ll probably get an error similar to this:
In order to fix it, edit this web.config. Find configurationSharePoint\SafeMode tag and change the MaxControls attribute to a bigger number. Once you do this, reload the page. It should help.