Thank you for the feedback. Actually we are planning on revising the requirements page very soon, with one of the upcoming releases. In the meantime you can safely consider FF4 as supported, since we haven't had any known issues with it, same would go for IE9, as the number of known issues is very small and we are currently working on fixing them. Please let us know if you need any additional information. I'll be glad to help.
the Telerik team
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