Help page claims:
Begin an input block with %html and it will be output as HTML. Use the <sage>...</sage> tag to do computations in an HTML block and have the typeset output inserted. Use <$>...</$> and <$$>...</$$> to insert typeset math in the HTML block. This does not require latex.
The html function clearly doesn't properly deal with the < and >.
sage: html(r'let <$>K = \mathbb{Q} 17 (\sqrt{-2})</$>')
<html><font color='black'>let <<span class="math">>K = \mathbb{Q} 17 (\sqrt{-2})</</span>></font></html>
sage: html(r'let <$$>K = \mathbb{Q} 17 (\sqrt{-2})</$$>')
<html><font color='black'>let <<div class="math">>K = \mathbb{Q} 17 (\sqrt{-2})</</div>></font></html>
The output should be the same as
sage: html(r'let $K = \mathbb{Q} 17 (\sqrt{-2})$')
<html><font color='black'>let <span class="math">K = \mathbb{Q} 17 (\sqrt{-2})</span></font></html>
sage: html(r'let $$K = \mathbb{Q} 17 (\sqrt{-2})$$')
<html><font color='black'>let <div class="math">K = \mathbb{Q} 17 (\sqrt{-2})</div></font></html>
This is based on the bug report given on 8/25/08 by john.perry@usm.edu available at http://spreadsheets.google.com/pub?key=pCwvGVwSMxTzT6E2xNdo5fA
