fontSize and for that matter, css
fontSize Firefox/Netscape/NN 6 IE 4 Chrome/Safari/DOM 2 Read/Write Indicates the font size of the element. The font size can be set in several ways. A collection of constants (xx-small, x-small, small, medium, large, x-large, xx-large) defines what are known as absolute sizes. In truth, these are absolute only in a single browser in a single operating system, since the reference point for these sizes varies with browser and operating system (analogous to the old HTML font sizes of 1 through 7). But they do let the author have confidence that one element set to large is rendered larger than medium. Another collection of constants (larger, smaller) is known as relative sizes. Because the font-size style attribute is inherited from the parent element, these relative sizes are applied to the parent element to determine the font size of the current element. It is up to the browser to determine exactly how much larger or smaller the font size is, and a lot depends on how the parent element’s font size is set. If it is set with one of the absolute sizes (large, for example), a child’s font size of larger means the font is rendered in the browser’s x-large size. The increments are not as clear-cut when the parent font size is set with a length or percentage. If you elect to use a length value for the fontSize property, you will achieve greater consistency across operating systems if units such as pixels (px) or ems (em), instead of points (pt). Em units are calculated with respect to the size of the parent element’s font size. Finally, you can set fontSize to a percentage, which is calculated based on the size of the parent element’s font size. Example document.getElementById("teeny").style.fontSize = "x-small"; Value Case-insensitive string values from any of the following categories. For an absolute size, one of the following constants: xx-small | x-small | small | medium | large | x-large | xx-large. For a relative size, one of the following constants: larger | smaller. For a percentage, the percentage value and the % symbol. Default Parent element’s font size.