Textpattern CMS Template Tags , conditional category

Will execute the contained statements when an error exists with the comments.
Will execute the contained statements if a comment is being previewed.
<txp:if_custom_field />
Will execute the contained statements if one or more custom fields for a given article have content.
<txp:if_different />
Will execute the contained statement when the value differs from the preceding value.
<txp:if_excerpt />
Will execute the contained statements if an excerpt is associated with the article.
<txp:if_expired />
Will execute the contained statements if a particular article is expired.
<txp:if_expires />
Will execute the contained statements if a particular article has an expiry date set.
Will execute the contained statements if the displayed article is the first in the currently displayed list.
Will execute the contained statements if the current category is the first in the currently displayed list.
Will execute the contained statements if the current section is the first in the currently displayed list.
Will execute the contained statements if an individual article is being displayed.
<txp:if_keywords />
Will execute the contained statement if the current article's keywords field has one or more entries.