None, really, though by accepting a performance penalty you can embed many MiniVend tags inside of regular HTML with things like:
[pragma no_html_parse 0]
<A HREF="[href minivend_page]">Link</A>
<SCRIPT LANGUAGE=MV MV="set Action">
mv_todo=return
mv_nextpage=your_page
</SCRIPT>
You will probably have to edit MiniVend pages by hand.
Some HTML editors have a tag like <NOTOUCH></NOTOUCH> that defines regions which should not be wrapped or reformatted by the editor. You should use this.
Also, if uploading a page from a Mac or PC make sure to upload in ASCII (i.e. non-image) mode. If you ignore this, you can break your MiniVend catalog!