Dimensions: Width and Height in Css

Before moving on, it is worth mentioning two very important properties that can be declared
for any element—width and height.
It might seem a little patronizing to mention them, as their uses must seem obvious. However,
these two properties have already appeared in several examples, and will continue to be used
throughout the book.
Both properties are essential for setting specific heights and widths of elements. Consider
that an element will expand widthwise to fit its container and heightwise to encompass its
content—you will start to realize before long that, in some situations, a certain amount of
control is missing. By applying width and/or height rules, you can regain control.
Values can be given as a length, percentage, or auto. Note that all of these values can be
influenced adversely by other rules within the style sheet, and also by the (X)HTML elements
they might contain. For example, the resulting display can be affected by a number of knockon
values from margin, padding, border, or child elements.