Using the Right Tag for the Right Job - HTML5 Mastery: Semantics, Standards, and Styling - page 39

software residing outside of the website's domain. On this, use these with caution and
only when absolutely no other solution will work!
Content model categories
As stated in Chapter 1 , originally, elements in HTML could be roughly divided into two
categories: block and inline. The content model of one category or the other defined
what kind of content could be placed inside a particular element. For instance, inline
elements could not contain block elements. As HTML5 developed, these two types of
content did not adequately describe the behavior of the available HTML elements. The
WHATWG replaced block and inline with a larger set of categories, 4 which group ele-
ments based on their similar characteristics. Elements in each category have a similar
content model and must abide by the rules defining what kind of content it can have.
There are now seven major categories, listed in Table 2-2 .
Even these seven categories do not fully cover all elements within all contexts. For
instance, an element may not fit into any of these categories (the html element, for
instance) or may be referred to as transparent , meaning it inherits the category of its
parent element. Many elements fit into more than one category, in which case they are
said to have a hybrid content model.
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