The drawback with border is that you can only define "global" styles, widths, and colors. In other words, the values you supply for border will apply to all four sides equally. If you want the borders to be different for a single element, you'll need to use some of the other border properties. Of course, it's possible to turn the cascade to your advantage: to substitute a similar font.
This sets the size of the font. Thiscan be defined as an absolute size, a relative size, a length value,or a percentage value. Negative length and percentage values are notpermitted. The dangers of font-size assignment are many and varied.Some of these dangers are covered in Chapter 4, "Text Properties".
Almost as simple is this: the sum of the horizontal components of anonfloated block-level element box always equals thewidth of the parent. Take two paragraphswithin a DIV, for example, whose margins have beenset to be 1em. The content width (in other words,the value of width) of the paragraph, plus itsleft and right padding, borders, and margins, always add up to thewidth of the DIV 's

It's also acceptable for the lines to be "open" as shown in Figure 7-54.
WARNING
Borders cannot be applied to inline elements in Navigator 4.x or Explorer 4.x/5.x. Only Opera 3.x draws borders around inline elements, and it only caps the beginning and end of the it (usually) with selectors that list various table elements. For example, in order to get all your table content to be red along with your document's body, try this:
BODY, TABLE, TD, TH {color: red;}This will often solve the problem. I say "often" because it doesn't always work, for reasons that are poorly understood. Navigator 4 has the most trouble getting it right, but its failures are not consistent. The best minds in CSS analysis have yet to come up with a recipe for predicting Navigator's behavior,