Our suggestion to achieve the scenario you describe is to place the RadSplitter in a MasterPage so that all its content pages will use the same splitter. You want to persist the changes made to the splitter when navigating to the different content pages. That is why, you will need to store the splitter's state in Session/Database depending on the requirements of your exact scenario. I suggest you take a look at the Save/Load State on server
online example of the RadSplitter which demonstrates how to save/load the splitter's state using a Session object.
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the Telerik team
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