Oh I know Blackcat, was just goofying around with you. The preview post button is right next to the submit reply button. Unless your doing the quick reply option in which case you have the "Go Advance" button next to it.
Also, in case you haven't change it, go to your options in the UserCP and at the bottom change it to "Enhanced Interface - Full WYSIWYG Editing". I also prefer the forum skin Classic UBB style, it's more military-like.