Concurrent with spacer.gif, there was also a `<spacer type="block">`[1] tag that was in use at the time.
Working at a boutique design shop back then, I remember trying endless combinations of the spacer tag along with spacer gifs to try to ship layouts that were at least semi (and hopefully mostly) consistent cross-browser.
Having lived through those web dev dark ages, I'm pretty baffled by the resurgence of 'markup as styling'.