found the old DLL file & put it in a bin folder & it works, but if I had just found that part and deleted it in the aspx file and re-built the web app in Visual Studio, it probably would have worked just as well.  That's what I get for using old code and not looking at its dependencies close enough.  Anyway, hope this all helps someone. Re: Error ..Could not load the assembly 'App_Web_4giibxae'. Make sure that it is compiled before... Mate a thousand thank you's for your great help. I have to admit VS2005 is the most difficult and unforgiving application I have ever used. I did the same thing as you, I  overwrote an aspx file, and then suddenly some important DLL files went missing from my Bin folder and the same error came up. Luckily I found it again - 'App_Web_#####.dll' (by doing a massive search all over my comp) and dropped it back into the bin folder otherwise I would have been screwed. Unfortunatley this is the only way to fix the problem aswell. The other method your suggesting to exclude the 'inherits' statement and rebuild won't work, I tried that method aswell first time.