Each typeface has a unique tone that should produce a harmonious fit between the verbal and visual flow of your content. With the first versions of html, web authors had no control over typefaces (“fonts” in personal computer terminology). Fonts were set by the browser, so pages were viewed in whatever font the user specified in his or her browser preferences. Modern versions of html and css allow designers to specify typeface. This is useful not only for aesthetic reasons but also because of the differing dimensions of typefaces. A layout that is carefully designed using one typeface may not format correctly in another.
In specifying typefaces you should choose from the resident default fonts for most operating systems. If you specify a font that is not on the user’s machine, the browser will display your pages using the user-specified default font. Bear in mind, too, that users can set their browser preferences to display all pages in their favorite font.
Legibility on-screen
Some typefaces are more legible than others on the screen. A traditional typeface such as Times Roman is considered one of the most legible on paper, but at screen resolution its size is too small and its shapes look irregular. Screen legibility is most influenced by the x-height (the height of a lowercase “x”) and the overall size of the typeface.