HTML and CSS Reference
to be known are calculated into their fixed-width equivalents. When
these calculations are complete and the page is rendered, the result-
ing values are the used values. Though the naming is unfortunate, it is
these used values that are encountered when scripting CSS through the
getComputedStyle DOM API or viewing the computed tab in Firebug.
■ Actual values : After all the calculations are done and a browser has
processed the document, there are some occasions where the used
value cannot be rendered, so the browser must approximate the
used value, creating the actual value. This can occur when a fractional
pixel unit results from a calculation (50 percent of 99 pixels) or when
a low-color-depth, monochrome display isn't capable of rendering the
exact color calculated.
There are three main types of element types in HTML documents
(a broad generalization) whose intended content types dictate their
behavior in CSS and presentation. There are elements that serve as
containers for other content ( <div> , <p> ), there are elements that differ-
entiate types of text content ( <a> , <strong> ), and there are elements
that refer to external content ( <img> , <object> ).
Throughout this topic the first type are block elements , the second type
inline elements , and the last inline replaced elements .
The World Wide Web Consortium (W3C) along with other standards
bodies such as WHATWG and IETF produce standards and specification
documents for everything from CSS to the HTTP protocol that computers
on the Internet use to communicate. You can find the specifications for