(everything below applies to the case when RadGrid has scrolling enabled and its height is set in percent)
There are a couple of examples, which show how to make RadGrid resize automatically together with the browser window. Indeed, they are simple, but demonstrate the general idea, which is missed by the majority of people, namely - you have to obey the CSS specifications with regard to percentage heights:
method to the RadGrid client object.
The following demo exists to show how explicit heights are required by the RadGrid parent elements, when the control is 100% high (any percentage, actually):
In addition, one has to keep in mind that RadAjaxManager generates update panels, which are <div>s with no styles. They break the layout from the above code library example, that's why the following example shows how to add a 100% height to update panel <div>s at runtime:
You should be able to construct your web page to work as expected, base on the provided information. There is one exception though - if you update the RadGrid control with AJAX, while the RadGrid's containing PageView is not the active one, and if RenderSelectedPageOnly="false" for the RadMultiPage (by default), you will need to call repaint() to the RadGrid client object once its PageView becomes active. For this case you can use the RadTabStrip's OnClientTabSelected event handler.
the Telerik team