gvim questions

[Omar Campagne <ocampagne gmail com>]

Hello everybody:
I'm just learning how to use gvim to edit po files, and  I've ran a
couple of msgfmt within the po, intentionally typing mistakes and so to
see what it detects. Also converting to html, which outputs the same
mistakes found by msgfmt.
My question is, with labels such as <quote> whatevever </quote> lets say
I typoed <quote> whatever <quote>.
Filetype, syntax and ftplugin are all on.
How can I detect those mistakes? <S-F12> doesn't "see" those mistakes.

Thanks,

Omar