To block the single ad at the bottom of the page? Seriously? I almost never even see it to begin with. I'm trying to find out whether or not this is permitted, but let's look at this from a moral standpoint while I wait for the answer.
We all use this forum free of charge. However, it's not free of charge for Carl to maintain and operate it. Servers cost money, and he invests an incredible amount of his own time tweaking and revising the forum software as well as writing the HTML for the guide. Other people help him out by writing articles, but in order for them to show up as a webpage, every last one requires his personal attention.
So...how often do you click that button up in the right hand corner with the word "Donate" on it? That's a rhetorical question, by the way.
That single ad at the bottom of the page makes it so he doesn't have to charge a fee in order to keep this site open. Why would you want to block it? As far as website advertising goes, it's rather non-invasive and out of the way. Why do you feel the need to block it?