ASP.NET AjaxControlToolkit with IE9 Beta

When I use the ASP.NET AjaxControlToolkit with the ToolkitScriptManager in Internet Explorer 9 Beta I get on every asynchronous postback javascript errormessages like “Invalid set operation on read-only property”. Adding this HTML-Metatag

[cc lang=”html4strict”][/cc]

should fix it. But this is just a workaround not a solution.

ASP.NET Forums Thread:

AjaxControlToolkit Issue-Tracker:

Read More