[your24hourstore]

its just alt text for the software.
goto stylevar/Style Manager/
under style manager drop down open edit templates, and open the header template, if you delete it you will have some problems, and be aware that any future updates may rewrite it or force you to revert to the old template, even because of this small rewite, so best you can do without really knowing what your doing is just rename the vb part to your site name, makeing sure not to modify

PHP Code:

     <div><a name="top" href="{vb:raw vboptions.forumhome}.php{vb:raw session.sessionurl_q}" class="logo-image"><img src="{vb:stylevar titleimage}" alt="{vb:rawphrase x_powered_by_vbulletin, {vb:raw vboptions.bbtitle}}" /></a></div> 


put your info were the old info is like powered_by_yoursiteinfo.