Why using pt and px to specify font sizes in IE can be a bad idea.

IE does not allow rescaling of text that has been specified in points or pixels. One downside of this is that vision impaired users cannot enlarge this text and nor can people using a low resolution display reduce it. To see an example of this under IE, try using View->Text Size to enlarge or reduce the text size. If you do not have access to IE, you can see some screenshots of font resizing.

12pt.

The quick brown fox jumps over the lazy dog.

12px.

The quick brown fox jumps over the lazy dog.

100%.

The quick brown fox jumps over the lazy dog.

1em.

The quick brown fox jumps over the lazy dog.