Hi shikha bansal,
RadFormDecorator is optimized to perform best according to every browser, and we cannot provide you with a solution for IE7, as all possible optimizations are already done.
As decoration is done entirely on the client, the script may be slowed down if there is a great number of controls on the page meant to be skinned. You can optimize the performance by limiting the number of controls that are to be decorated and by adding only the desired type of form inputs in the DecoratedControls property instead of using all or default.
the Telerik team