If you encounter this error while navigating away from an AJAX-enabled page with a non-IE browser, you can silence it with the following JavaScript:
{
window.onbeforeunload = function() {
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(ignoreOnEndRequest);
}
}
function ignoreOnEndRequest(sender, e) {
err = e.get_error();
if (err) {
if (err.name == "Sys.WebForms.PageRequestManagerServerErrorException") {
e.set_errorHandled(true);
}
}
}
Hope it works for you!