I have a relatively recent laptop with decent hardware and on Windows web browsing is pretty good, but when on ubuntu, it gets so slow, I can't watch properly a video from youtube or even low quality videos from elsewhere, which lag all the time. Also images take more time to load. I've tried everything, my firefox has adblock plus, flashblock, I use flashgot to download videos and watch them on a player but I can't be downloading several MB Long videos all the time. I've tried Chromium, Firefox and Opera, Opera is the one that allows me to have more tabs open without freezing, however Flash problems remain. Chromium crashes all the time with the "aww snap" page.
On an older PC I have with Lubuntu, it's even worse, I can't open a window with a video because it will freeze the system entirely until it loads, I often have to go to windows XP if I want to browse decently. What can I do to have a better web experience?