Currently we are aware of one issue with the framework and IE10 that may cause the page to break.
The issue is in Microsoft's libraries, and it cause MicrosoftAjaxWebForms.js not to be included in the scripts. We rely on these scripts, the Sys.WebForm.PageRequestManager is used inside the initialization of some of the controls, and since it is not included they will not work properly.
In general the ScriptManager (and RadScriptManager in particular) relies on some .NET functions about detecting browsers and browsers versions. The IE10 is not detected properly and as result the MicrosoftAjaxWebForms.js is not referenced in the output HTML page and it is not requested and loaded by the browser.
There is a .NET fix about this problem, install it on your server and it should work correct:
, I would also suggest you to keep your .NET up-to-date since there could be another issues in Microsoft's code that we are not aware of.
For any rendering issues with the Windows 8 and the browsers you mentioned I would suggest you to open a regular support ticket and send us sample ruinable example which demonstrates the problem, Thus we could test them locally and do our best to isolate their root cause.
the Telerik team
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