HTML :td (OT)

[Tyler]

Just for the record: width can be specified in either absolute terms
(ie, exact measures) or relative terms (eg, the width of an "M" for
whatever font of whatever size is being used for display)

absolute units - in, cm, mm, pt, pc
relative units - em (width), ex (height), px
percentage - relative to parent's width

If you specify a width as being 20em, it won't matter WHAT font size
or type the user may have overriden your style with, the element's
width will still scale to twenty maximum-width characters.

For this reason, web design should always attempt to use relative
units as opposed to absolute for layout.  If your navigation column is
always 30em wide and your content column is fluid (or, preferably, has
a min-width or spacer in it to guarantee a minimum width), then you
never need worry about the browser font size and style settings; it
just scales automatically.

Tyler