I put together for an internal customer onto a SharePoint 2007 publishing site back in 2013. This features the CSS only buttons designed by James Norman, which were originally built for another site while we were working together.

The design called for the buttons to be far down on the page, with the tooltips hovering above. Originally written for for IE 8 using HTML 4.01 transitional, the effect itself is made up of 4 CSS classes and 11 or so lines of JavaScript. I have tested the effect in the latest major browsers, and it appears to work just fine.