please bump to a newer version, the one in portage is now nearly 2,5 years old
The Tidy project's version scheme is very opaque, but here's the SVN revision info: http://tidy.cvs.sourceforge.net/tidy/tidy/src/version.h?view=markup
The project has been active, adding new features and fixing bugs, but by "hiding" progress in SVN (versus releasing "stable" version tarballs), it is no wonder that Gentoo hasn't updated it in a long time. That said, I hope to see updates soon! :)
From the Tidy news, since last ebuild update:
'18 June 2008
The configuration option anchor-as-name has been added.
13 August 2007
The configuration option merge-spans has been added.
14 June 2007
The configuration option sort-attributes has been added. Additionally, the option show-body-only has been extended to accept "auto".'
+ 22 Jul 2009; Robert Buchholz <firstname.lastname@example.org>
+ +files/htmltidy-20090325-tidyrc.patch, htmltidy-4.8.6.ebuild,
+ htmltidy-5.10.26-r2.ebuild, +htmltidy-20090325.ebuild:
+ Version bump to latest CVS sources. Remove xml use flag and html2db as it was
+ never integrated upstream and does not compile due to usage of internal tidy
+ API. Enable /etc/tidyrc and ~/.tidyrc config paths and build autotools
+ properly, closes bugs 154834, 219450, 226437 and 278604.