The Atom feed fails validation at http://feedvalidator.org/ because the `<category>` tags are syntactically incorrect ([spec](http://www.atomenabled.org/developers/syndication/atom-format-spec.php#element.category)). With this patch it validates.

    Index: templates/atomitem.tmpl
    ===================================================================
    --- templates/atomitem.tmpl     (revision 2640)
    +++ templates/atomitem.tmpl     (working copy)
    @@ -8,7 +8,7 @@
            <link href="<TMPL_VAR PERMALINK>"/>
            <TMPL_IF NAME="CATEGORIES">
            <TMPL_LOOP NAME="CATEGORIES">
    -       <category><TMPL_VAR CATEGORY></category>
    +       <category term="<TMPL_VAR CATEGORY>" />
            </TMPL_LOOP>
            </TMPL_IF>
            <updated><TMPL_VAR DATE_3339></updated>