In versions prior to Q2 2008, I could never get MarkFirstMatch to work with Opera (I'm running 9.27 of Opera). It wouldn't let you type enter in the box. So I just set MarkFirstMatch to false if the browser was Opera. After updating to Q2 2008, I decided to check to see if this was fixed. It now lets me type and hit enter, but there are still issues. Inside of an UpdatePanel, I have three combo boxes, each with their own ObjectDataSource. The SelectedValue of the first is used as a SelectParameter for the second and third. The SelectedValue of the second is used as a SelectParameter for the third. If I type in the third and press enter, a button after it in the aspx gets pressed (this doesn't happen in other browsers), and both the SelectIndexChanged event and the button's clicked event occur. If I type in and press enter in either of the first two, all appears normal in terms of the events that occurs server-side, however client-side the third combo box's items are not updated (also the second's items are not updated if I type in the first). Whatever I click on next produces a SelectedIndexChanged event to occur server-side, since the contents of the box Client-side (and the SelectedIndex) don't match what the server-side thinks is there.