It looks good to me, though if you could give us a link to the forum we'd be able to tell you for sure (if you copied+pasted the code then there should be no problem).
If you need help moving the ad code elsewhere (ie. the footer, or above the forum), PM me and I might be able to help.
If they have purchased IPB then they would have a version that is above 1.3, as 1.3 was the last ever free version of Invision Power Board they made, now its all paid for.
Version 1.3 seems soo long ago but it wasnt long ago that they had 2.0.2 and all that come out, and now they are nearlly upto 2.1.6 - and somehow they find they can fix heaps of issues/bugs with each release which amazes me, you'd think they'd run out of things to correct :S
The reason they don't run out of things to fix is because everytime they fix one bug they risk introducing another. It's a common problem in software development.
But yeah, the ad on your site looks fine. In the forum menu at the top of this page, there is a link to the ad code under "Quick Links" if you don't already have the correct code.