I have almost the exact same question as at the following post (and I tried both of the answers, but neither works), except I'm not worried about whether the TabContainer is last on the page or not - I want to prevent the page from skipping up or down to any tabcontainer when the updatePanel containing the tabcontainer gets updated. (Of course, I guess it's actually a TabPanel - the active one - getting the focus, not really the TabContainer.)
AjaxToolkit: the last TabContainer on the page is focused on page load
As the poster says at above link, I have not explicitly set any focus, so I don't know why focus is getting set to my tabPanel. When I debug, I can see that there is some javascript loaded by Ajax that sets focus.
I guess what I want to do, unless there is some property I can set (autofocus=false ?) is override whatever ajax javascript is being executed so that the focus does not get set.
Not sure how to go about this, however. Is that javascript source published somewhere, so I can copy it, comment out the focus instruction, and override?
UPDATE
I was debugging the release version of the ajax script. I didn't realize there was a debug version available. I had debugging on in web.config, but apparently the ScriptManager also needs ScriptMode="Debug"; when I set that, I get debug versions of internal ajax code. I'm not done yet, but I think should now be able to find the offensive code that sets the focus without me asking it to set any focus, and override it. I'll post an answer when I'm done.