When describing length and width values in HTML and XHTML, values follow three conventions:
Pixel values are written numerically. So, if you want to have a table be 500 pixels across, you'd simply write:
As with colors, length values are presentational and are used in transitional documents. Style sheets are the current recommended method.
Percentage values are written numerically with a percent sign following. If you want your table to take up only half of the available screen space, you could write:
Relative sizing in the context of length values is a means of sizing something by having any leftover length be distributed appropriately. A good example of this is with frames, where you can use the "*" symbol to indicate that any remaining available space will be allotted accordingly.
Because length values are written numerically, they are considered to be case-neutral.