There are many different measures you can use with your font sizes. But most people just use pixels or points and don't think any more about it. However, by doing that they may be causing problems for some readers. It's important to think about how your site will be used and the audience before you decide on what font measure to use.
Fixed Height Font Measures
There are several absolute or fixed-height font size measurements:
- inches (in)
- centimeters (cm)
- millimeters (mm)
- points (pt)
- picas (pc)
But absolute font sizes aren't generally good for Web pages. The only time you should use absolute font sizes is if you're writing a style sheet to print out your Web page - in other words, the Web page will be a fixed size on the paper.
Relative Font Measures
Relative font sizes size the font based on the value of another length property. Relative font sizes include:
- Ems (em)
Based on the default preference set in the customer's browser
- X-height (ex)
Based on the height of the lowercase x character.
- Pixels (px)
Based on the resolution of the screen.
- Percentages (%)
Like ems, based on the default preferences of the browser
Most people prefer points, as they think that they will get a more precise page layout that way and most print designers are more familiar with points. However, Macintosh and Windows computers display points differently because the two machines have a different DPI. Also, Netscape 4.7x doesn't display pixel values correctly on either machine. So, it's not a good idea to use points.
My Font Preference
I prefer to use ems or percentages. That way, I'm not affecting the usability or accessibility preferences of my readers, but they are seeing my pages approximately as I intended them to.