After an investigation of the way URL are dealt with in LyX,
it seems that the export to LateX looses the <URL>anchor structure
which appears in the popup: e.g. if I type in Lyx as the anchor («Name»
in the popup) and http://www.lyx.org/ as the url, this appears as
\begin_inset LatexCommand \htmlurl[LyX]{http://www.lyx.org/}
in the lyX file and
LyX \url{http://www.lyx.org/}
in the LaTeX file.
That's OK for the typesetting, but it's a pity to loose what is
needed to build a correct hyperlink: instead of
<A HREF="http://www.lyx.org/">Lyx</A>
we get using either tth or LaTeX2HTML
Lyx <A HREF="http://www.lyx.org/"><TT>http://www.lyx.org/</TT></A>
I solved this with postfiltering, but it seems a bit awkward and it
replaces the nice popup by ERT.
--
Jean-Pierre