Some information about .NET 2.0 and client side validation.
As opposed to .NET 1.1, .NET 2.0 does not rely on ready-made .js files in the aspnet_client folder in order to make client side validation.
Instead the files is made run-time. .NET 2.0 does this by adding a reference to a webresource.axd file in the root of the web site.
The .js is generated by this axd so that it matches the browser and the controls on the page. The reference can look like this:
In order for this to work with Sitecore 5.2, you must add the WebResource.axd to the IgnoreUrlPrefixes in the web.config:
The setting should be set by Sitecore as standard, but it is not yet so. So until that happens, remember to set it yourself, or you will get an “WebForm_PostBackOptions is undefined” error on pages using validators.