Even ads that only have images can slow the fastest connection to a crawl. What happens is that the ad company requires an iframe in the page that gets loaded up from the ad company's servers. What happens though, is that the ad company's connection isn't so great, and your web browser will not display the entire page until the ad company's server responds. I used to let advertising through when I browsed the web so that the sites I visited would get some money. After experiencing stalls from ads regularly, I stopped them entirely.
To stop ads entirely, get Firefox and install the AdBlock Plus and Flashblock add-ons.
I just downloaded Ad Block Plus. I’m looking forward to trying it!