[troyb]

What you're seeing is OmniWeb adjusting the position to allow for your tab drawer--it also bumps it down a bit from the top of the screen. No bug here though perhaps it is unexpected functionality.

On launch it should place the first window in the same spot unless you have a snapshot taken, in which case it will load that. Try closing all your windows and then choose "Take Snapshot" from the OmniWeb window.