Separating Content from Presentation
CSS and Accessibility
Use scalable rather than absolute units.
- Use em, percent(%), or keywords.
Try not to use pixels (px) or points (pt) for font and block sizes because the user cannot resize them. Note: Point should never be used for screen sizes anyway, though using it for print style sheets is acceptable.
Differences between Em and Percent
For current implementations of font-size there is not much difference between em and percent. For block-level sizes however, there is a large difference.
Don’t mix HTML colors with CSS colors
If you define your background-color with an HTML attribute, but define your foreground-color with CSS, then when style sheets are disabled, you may have conflicting colors that would make for unreadable text.