i wanted to remove ads from my join page but i wanted the ads to be set to global so they showed on profiles and everywhere else..

i went to join_index.html found - (ow_system_plugins/base/views/controllers/join_index.html ) and in the  style section of that html file i added 

{style}{literal}table .ow_automargin, .ow_std_margin{display: none !important;}{/literal}{/style}

this removed ads from join page only so you can still enable global ads yet they wont display on join page... 

this is only confirmed using a theme with no sidebar. hope this helps others wanting to not spam there potential members with ads right off the bat, it also makes your site look a bit more professional when first landing on a page with no ads.