A simple and practical hack that worked (and continues to work) identically across all browsers without the need for elaborate edge case code.
I'm curious, with the new libraries, can CSS yet do:
<table width="90%" align="center"><tr valign="middle"><td width="20" valign="top">menu</td><td width="100">leftcol</td><td width="*">content</td></tr></table>
But due to the IE6 dominance and abandonment it took many years before this part of css was broadly supported by browsers, so developers had to either use html tables (even when not semantically appropriate) or use hacks like floats (which was not designed for this) to achieve a table-like layout. So the age of hack was due to browsers not supporting css, not to to deficiencies in css as such.
That said, html tables never displayed identically across browsers before css. There were lots of corner cases e.g. with the interaction of fixed and flexible columns. Which is not really surprising since the display model for tables were never specified in the first place before css.
The delicious irony is that CSS had to emulate the old table model to overcome its default layout deficiencies. And IIRC it still can't natively handle mixing relative and fixed widths, and consistent vertical centering.
> html tables never displayed identically
My bread and butter used to be slicing photoshop comps into websites. My table layouts were pixel perfect on every browser without hacks. I do agree there were a few things that had to be accomodated using and spacer gifs - but it was painless compared to elaborate and fragile CSS hacks.
I shouldn't still care about this stuff - I moved to IOS dev thank goodness - but I still nuture a burning hatred of CSS years later :)