WebResource.axd or ScriptResource.axd do not work!

So you have some embedded resources in your ASP.Net control library and you want to use them. But instead, nothing works. Scripts are not loaded and images are not displayed.

Look in the IIS log files and check for an error like this: "Exception information: Exception type: ArgumentOutOfRangeException Exception message: Specified argument was out of the range of valid values. Parameter name: utcDate".

If you see it, then your assembly where the resources are embedded has the build date into the future! This also applies to the code you just built and the date is correct and the date of the server where you want to copy it to is in the past. It also applies when the time is in the past, as when you are copying it on a server in a different timezone!

Update: There are other reasons why axd files are not loaded. One of them is that some other IHttpHandler (defined in web.config) is messing up with your settings.

Another is that the .axd extension is not defined in the virtual directory mappings (You get the dreaded Webform_PostBackOptions is undefined javascript error). Go to IIS manager to the properties of the virtual directory, click on the Configuration button, select the Mappings tab. You have to have the axd extension defined to open with aspnet_isapi.dll. Warning: there is a checkbox in the properties for the extension mapping called Check that file exists. Make sure it is unchecked, as the WebResource.axd and ScriptResource.axd are not actual files, so the mapping will fail if the check is set! On Windows 2003 there is also a listbox at the bottom of the Mappings tab. Edit it and look for yet another Check that file exists checkbox and, of course, uncheck it.