In version 2011 Q1 the "resize:none" css rule is added to the default CSS for RadTextBox textarea, so now the textbox is not resizable by default due to valid reasons. However, in RadInputManager we keep the resizable attribute for the browsers which support it, as it is a User Agent feature.
If the "resize:both;" is enabled, you can limit the resizing size with "max-height" and "max-width" CSS attributes.
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