If you guys are using affinity settings, don't forget to set other running processes to use a different core. Typically all are set to have access to any core. By changing the browser to use a specific core, all other programs are still allowed access to that same core. If you really want to tweak it, set everything else to use one core, and the game browser to use the other core all by its lonesome.
If you restrict your browser to the 2nd core, and all other processes still have access to that 2nd core, you can actually decrease your performance.
Take a look at the priority settings too - these are actually a more efficient way of giving processing rights. Restricting core access is risky business, especially when multi-core cpu's are designed to hand out work to the lowest utilized core to begin with.
Don't forget also - whenever you set affinity or priority... those settings are lost once you close that program. You have to reset them each time you start that particular program (browser, etc). There are programs to monitor this for you and set them automatically, or a guy could create a script to do this as start up, but then its just more stuff running...
** edit **
anyone using firefox might also want to check out this thread for how it is handling flash (among others) within containers.