I apologize for lack of details, given I was offline at the time of today's incident, but I will explain to the best of the Administration's knowledge what happened today.
First off:
Earlier today, a user uploaded quite a few very unpleasant images, to which he attached to several mainstream templates. To which, these images were put on a large number of pages across the site. As of a few hours ago, all images and templates in question have been removed or fixed, thanks to quick action on the part of a few outstanding contributors and the Administration.
There are reports that the caches have not updated on all pages, allowing some users to still see the questionable images. To alleviate this problem, please follow the following instructions:
Clear your catche
* Internet Explorer: hold down the Ctrl key and click the Refresh or Reload button, or press Ctrl+F5. * Firefox: hold down the Shift key while clicking Reload; alternatively press Ctrl+F5 or Ctrl-Shift-R. * Opera users have to clear their caches through Tools→Preferences * Konqueror and Safari users can just click the Reload button. * Chrome: press Ctrl+F5 or Shift+F5
If you wish to inquire about more information on the matter, or require..well, anything really, follow the instructions to join the Internet Relay Chat channel #Halo-Nation or #Halopedia.
Comments, questions, and concerns below. Thank you.
[Sometimes, it's all about the glory.] 
[Put your boot up enough alien backside and the corps will pin rows of medals on your chest.][Bad ass, unlocked.]