in reply to black tags
highlight the black stripe to see the text
<th>You can see this header
<td bgcolor='#000000'><font color='#000000'>
You shouldn't see this text </font>
<table><tr><td bgcolor=#000000><font color=#000000>
Hidden text here
Having a black tag (or something similar) would be easier and would probably be used a lot.
The <black><obscure> (I like the suggestion, ww) tag could also be translated to a <span> or a <div> with a certain CSS class. This would allow those of use who want to cheat without a lot of effort to modify our style sheets accordingly. :-)
Unixish Shell Scripting languages
Other (post in comments)
Results (377 votes). Check out past polls.