We had an interesting internal discussion around Internet Explorer Mobile and how it handles Pop Up Windows. I thought I'd share it as I simultaneously was approached by a customer who had similar questions/concerns.
Pop ups are usually implemented using window.open. IE Mobile will support window.open only if the user directly initiates an action that causes script to call window.open. For example, if the page has a link and script to open a new window when that link is clicked, window.open will work when the user clicks the link. But if the page’s script calls window.open on an onload event, window.open will not work. So pop ups are prevented.
When window.open is allowed to work, it will load content in the same window because IE Mobile does not support multiple windows.
I know many people really want IE Mobile to support multiple windows so I realise this is a double-edged sword....