The display of lists (eg for a taxonomy term) sometimes goes horribly wrong.

Here is one possibility.

The problem is with teaser truncation. Our authors can use most html in particular they can open their post with the html tag 'table' and similar. They, of course, close their tags and all is well. However, when we go to a list view (say rendering a term in the taxonomy), a list of teasers is provided, in particular the teasers often are the truncated first 600 characters of a post. And sometimes that includes an opening 'table' tag but no closing one. Then the tpl.php of the theme etc start putting opening and closing 'Divs' around the list items. But that then gives you a result where you have an opening 'div' an opening 'table' then a closing 'div' ie overlapping tags. A few of these the resulting page won't render and the whole lot falls over.

Solutions:
a) use the module Node Teaser and have an unproblematic teaser (I'm trying this successfully).
b) ban the use of 'table' etc tags (not practical)
c) run the open 600 characters of the post through a filter that removes bad stuff prior to forming the teaser (seems the right way to go).

Hope this helps someone!