Question

Since the latest Firefox update, we are getting a Sys.Webforms is undefined error on a website.

Asp.net, .Net 3.5, Aspx page containing ascx controls with javascripts attached in the ascx OnPreRender with ScriptManager.RegisterStartupScript.

Sys is defined but Sys.Webforms remains undefined also in the Sys.Application.add_load and $(document).ready.

It looks like, but not 100% sure, that this happens only over https.

No other browser reproduces this error.

The error happens in this part of the attached script:

Sys.Application.add_init(AppInit);

function AppInit(sender) {
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(that.onBeginRequest);
}

Any idea would help.

Answer 1

As it turns out, 51degrees.mobi premium device data file was the culprit.
Deleting the file, thus not loading definitions from it, solves this problem.
It looks like our version is not handling firefox 14.0.1 user agent string well.