One last hint:
If your website was working fine before you edit the ASP page (or the code behind), it's not necessary to change anything in the web.config. Just leave it alone.
Mr. Azim's recommendation is crucial from performance point of view.
web.config in your production server must always have debug="false"
in the compilation tag:
<compilation debug="false" strict="false" explicit="true" targetFramework="4.0"/>