12  HTML and output

12.1  Formal HTML validation

TTH takes as its standard HTML that can be rendered by Netscape and IE browsers versions 4 and higher (with the caveats above). The formal standard that TTH-translated documents follow is strictly HTML4.0[1]8 Transitional. However, TTH does not formally validate its documents, and can be made to violate the standard by some TEX usage.
One reason for violation arises because HTML4.0 requires a <title>...</title> for every document. A title is constructed from LATEX files that contain the \title{...} command, in which case HTML conformance is ensured by putting the \title command before any text (i.e. in the preamble, where it belongs). If the \title command is not desired in the TEX file, for example because it is a plain TEX document, a title can be provided by the author for the HTML document by putting a line like this at the top of the TEX file.
%%tth:\begin{html}<title>Put the title here</title>\end{html}

This line will be ignored by TEX. Actually, any raw HTML output at the start of the file is assumed by TTH to indicate that the author has explicitly output a title. If no title indication of any of the above types is present, TTH attempts to construct a title from the first few plain words in the document, in much the way that the first line can become the title of a hymn.
If commands like \item, that output material to the HTML file occur before the title has been constructed, the HTML title command will be out of order and the formal standard will be violated.
In the case where the title construction fails, or if some other TEX usage causes a violation of the formal standard, browsers will still render the output correctly if this manual is followed.

12.2  HTML Styles

There are good reasons why the <head> and <body> tags are by default omitted by TTH. See the FAQ [B.3] for a brief discussion. However, the evolution of HTML standards (not yet browsers) is towards imposing more restrictions on the freedom to omit tags. For example XHTML requires that containers have both opening and closing tags. Therefore TTH has a switch -w? (where the question mark denotes an optional integer) that controls its writing style as follows.
Construct title. Do not enter head and body tags.
-w -w0
Do not construct title or enter head/body tags.
Enter head and body tags assuming that the title is the dividing point.
Use XHTML syntax.
Don't use block level font size commands between paragraphs.
At present, in addition to the default style that attempts to construct a title but does not enter head and body tags, -w or equivalently -w0 prevents TTH from attempting to construct a title or anything else in the way of head/body divisions. This style is best used for documents where the author has explicitly entered the required HTML tags. The switch -w1 invokes pedantic HTML style which enters head and body tags under the assumption that the title (possibly constructed automatically) is the last thing in the head section. A style -w2 produces XHTML documents but requires cascading style sheet (CSS) support in the browser otherwise the rendering will not be as satisfactory as the default.
Addition of four to the writing style index (e.g. -w4) prevents TTH employing block-level font size commands if the size is changed immediately after a \par or implied paragraph. The additional CSS style sheet is not inserted and, of course, the browser need not support CSS. The (now) default writing style is to accommodate tables and equations inside sections of larger or smaller text in a manner that will pass standards validation. According to the standard, HTML font changing commands like most others, are either of inline type, in which case they are forbidden to contain block level constructs like tables, or block type, in which case they force a new line and so can't be used within a paragraph. The default can't universally fix this unnecessarily restrictive requirement of the standard (which most browsers wisely do not honor). There are situations where TEX usage is simply impossible to express in HTML. However, it does fix the vast majority of sensible usages. The switch -w4 turns off this approach, reverting to less standards-compatible style.