In Opera: right click anywhere. Select Block Content. Click on any annoying banner ads which tries to find a block pattern. No default filter like AdBlock, but pretty easy and a core element of the browser.
I'm an Opera user on Linux because I found it somewhat faster than Firefox back N years ago but I'm not sure I'm hanging on to Opera out of anything but loyalty and stubborness. Both Opera and Firefox (which is better at handling Gmail) bloat up to awful amounts of memory with time (why is Opera using 400 megabyte RSS now after 3 days?))
Firefox still is awefully slow on Linux. I switched to Opera rather recently (~6 months?) because of this.
Thanks to Opera's amazing session saver and the quick end/restart cycle I find it much less a pain in the backside than Firefox if it gets hoggy (not that it ever did that for me, sometimes it slows down for some reason though).
You should try Chrome nightlies for Linux. It seems much faster than Opera 10 or Firefox 3.6apre1 for me and it uses much less memory for large amount of tabs.
I'm an Opera user on Linux because I found it somewhat faster than Firefox back N years ago but I'm not sure I'm hanging on to Opera out of anything but loyalty and stubborness. Both Opera and Firefox (which is better at handling Gmail) bloat up to awful amounts of memory with time (why is Opera using 400 megabyte RSS now after 3 days?))