Different systems have different, but similar font definitions. To address this, CSS allows you to specify a comma-separated list of font names. Names that contain spaces (e.g., "Helvetica Neue") must be enclosed in quotes, while names without spaces don't need the quotes. The list of font names is processed left-to-right, until a font name is matched. Thus, the list defines a "fallback" sequence... i.e., if "Helvetica Neue" is not found, try "Helvetica", then "Arial", and finally "Lucinda Grande". If no matching font is found on your system (unlikely, but still possible), the browser will fall back to it's own default font choice (often, but not always, a "Times Roman" serif-ed font).
"serif" and "sans-serif" are generic names that always correspond to *some* installed font, so it is often sufficient to just specify the one font name, rather than a whole list of font names
TiddlyWiki syntax allows you to wrap any content (not just table cell content) using @@.classname ...@@ syntax. The ".classname" refers to a CSS class defined in a stylesheet tiddler (a tiddler tagged with "$:/tags/Stylesheet", containing CSS declarations). Note that, in the above TiddlyWiki syntax, there is a *space* following the classname... this is important, as it signals the end of the classname and the start of your content. Everything following that space, up to the closing "@@" is content, that will be styled using the declared classname.
Alternatively, you can also use CSS definitions directly "inline", rather than defining a classname in a separate Stylesheet tiddler. For example, using the standard CSS text style "color", you can write:
@@font-family:Times New Roman;font-weight:bold;color:green;background-color:yellow; THIS IS A BOLD, GREEN, AND SERIF-ED FONT@@
Note also that items of inline CSS are separated by a semi-colon (;) and, unlike the .classname example above, the CSS does not *require* a trailing space, as long as the content that follows it does not match any valid CSS syntax. Even so, it's a good idea to *always* include the trailing space to ensure that the end of the CSS syntax is clearly defined, regardless of the text content that follows it.
hope this helps,
enjoy,
-e
Eric Shulman
TiddlyTools.com: "Small Tools for Big Ideas!" (tm)
InsideTiddlyWiki: The Missing Manuals