I never noticed any slow-down. In fact, sites download faster if their advertising isn't downloaded along with the good stuff.
If your browser allows making custom settings for individual sites, it helps to turn off scripting if you notice a lot of activity after the page supposedly stops loading. And disallowing cookies except when absolutely necessary is also a good idea. My browser is Opera, and it allows me to make custom settings for each individual website. Firefox is also pretty good but not as flexible as Opera.
In faith, Dave
God doesn't want weekend visits. He wants full custody.