The class attribute specifies default text-formatting options. It is overridden by the class attribute of a span element within the block. Valid classes are:
Typically, "title" might be rendered in larger type, "subtext" in smaller gray type, "article" in a serif typeface, "link" in blue, "subdued" in gray, "important" and "negative" in red, and "positive" in green. But these interpretations are not guaranteed to be consistent among renderers. In some implementations, "description" and "small" appear as normal text. The "value" class is used implicitly for template layouts.
Classes can be combined (e.g. <block class="title link"> or <block class="title article">). If incompatible classes are specified (e.g. <block class="important subdued">), the last one takes precedence.
The halign attribute works only in blocks that occur directly under a module. In other contexts, e.g. within a header or placard, the attribute is ignored.
Whitespace in a text block is handled as in HTML: In an unbroken sequence of whitespace characters, all but the first are ignored, as are whitespace characters at the beginning or end of the block. Do not attempt to format text using spaces, tabs, or line breaks.