I have a navigation menu acroos the top of my employer's website. All of the links, etc, are gifs, so I can specify the height of the table to the exact pixel, without having to worry about cross-browser font size problems. The top nav table is in it's own positioned <div>, and the main content table is in a separate, precisely positioned <div>, so the top of the body table rests JUST up against the bottom of the nav table.
In Opera5/Mac, the nav table slightly overlaps the top of the body table, cutting off the tops of my page header text. Bleaugh.
Specifically: I have two table rows with blue cell backgrounds and no bgcolor for the table itself (the cells look like buttons). Each row/cell is specified at 17px high. The button table has zero borders, zero cell padding, and 5px cell spacing. It adds up to a 49px high table. The table is specified at 49px high. It is nested inside a 49px high cell of a larger table.
In Opera5/Mac, each 17px tall blue table cell appears to have a few extra pixels added, increasing the height of the overall header, and overlapping my body table... (See occupation URL in profile for example)