It's likely it could be delays caused by Flash based ads trying to load. First make sure your Flash is up to date. Go to
http://get.adobe.com/flashplayer/ and download the latest player. When you start the installation make sure you have quit your browsers (Safari, Firefox etc). This may improve things. Otherwise to really speed up install free ClickToFlash (OSX 10.6 or earlier)
http://clicktoflash.com/ or for OSX 10.7 click Safari in the menu bar, then extensions, then scroll down to ClickToFlash and click Install Now.
ClickToFlash stops Flash loading automatically. If you need to run Flash (movie, game etc) Just click on the section you need. No other Flash parts will load (ads etc.)