Should you use X-height?
Another relative unit that you can consider using is x-height, which is the height of the lowercase letter x.
I don't recommend the use of x-height, unless you are an expert typographer and will understand how text set with a particular x-height is likely to be interepreted by users who do not have the font specified installed on their machines.
Without undue care and attention, using the x-height to specify text size, could result in text that is difficult to read on some browsers.
Index | Next: Using absolute size keywords