5 Here are some proprietary tags that W3C does not define but occasionally show
6 up in the wild. We have only included tags that would make sense in an
9 <align>, block element that aligns (extremely rare)
10 <blackface>, inline that double-bolds text (extremely rare)
11 <comment>, hidden comment for IE and WebTV
12 <multicol cols=number gutter=pixels width=pixels>, multiple columns
14 <spacer align=* type="vertical|horizontal|block">, whitespace in doc,
15 use width/height for block and size for vertical/horizontal (attributes)
17 <wbr>, potential word break point: allows linebreaks. Only works in <nobr>
19 <listing>, monospace pre-variant (extremely rare)
20 <plaintext>, escapes all tags to the end of document
21 <xmp>, monospace, replace with pre
23 These should be put into their own Tidy module, not loaded by default(?). These
24 all qualify as "lenient" transforms.