HTML and CSS Reference
• The content may be a set of grammar rules that defines the order
and nesting of tags within the defined element. You use this con-
tent type when the tag being defined contains only other tags,
without conventional content allowed directly within the tag. In
HTML, the <ul> tag is such a tag, as it can contain only <li> tags.
• Mixed content, denoted by a comma-separated list of element
names and the keyword #PCDATA , is enclosed in parentheses. This
content type allows tags to have user-defined content, along with
other markup elements. The <li> tag, for example, may contain
user-defined content as well as other tags.
The last two content types form the meat of most DTD element declar-
ations. This is where the fun begins.