Replace .forum_list with the name of the template.
Use FireBug to inspect the code.
http://xenforo.com/community/threads/frequently-asked-questions.5183/#post-181112
How can I find out which template to edit?
Using your browser, view the page source and look for a line of code near the top of the page which begins
<div id="content" class="; the class is the name of the template. So for the main forum page, the line of code is:
<div id="content" class="forum_list">, which makes the template
forum_list.