Hi,
If dialog is located inside of a container and page has some elements with position:absolute/relative, then problems with rendering order may happen. WebDialogWindow is not able to get around them, because those are rendering rules of a browser.
The best solution- is to keep dialog directly on main page preferably as last control in form. If that is not possible, then application may try to process ClientEvent.Initialize and move dialog-element to "a better" container, for example to body.Below is example.Note: if similar action will trigger some side effects, then that approach should not be used.
function initDialog(dialog, evtArgs){ var elem = dialog.get_element(); elem.parentNode.removeChild(elem); document.body.appendChild(elem); //dialog.show();}</script><div style="position:absolute;left:200px;top:200px;width:300px;height:300px;overflow:auto;background:cyan;"> <ig:WebDialogWindow ID="WebDialogWindow1" runat="server" Width="300px" Height="300px" Modal="true" WindowState="Hidden"> <ClientEvents Initialize="initDialog"> </ClientEvents> </ig:WebDialogWindow></div>