Allow user settings to define base text size
Typographic conventions tell us that the optimal text size for readability is somewhere between 10 and 12 points. Printed documents generally follow these conventions and satisfy the average reader under typical reading conditions. For the nonaverage reader, there are reading aids, such as glasses and document enlargers, or large-print editions.
The Web is different. Web users can set their browser to display text at an optimal size, based on their needs and environment. Some users require type that is larger than average for reading. Some may need to enlarge text so a Web page is readable in a group setting. Others might want the text as small as possible so they can read it on a PDA or cell phone display.
In designing text, the base text size should be a decision left to the user. All other text elements should be sized relative to the user-specified default. This approach allows users to establish optimal settings in their browser preferences and to have those settings apply on all sites that they visit. If each site has a different base text size, users must continually adjust their text settings as they move from site to site (Figure 3.3).