In the past couple of months, I started noticing that my MacBook Pro would slow down to almost unusable speeds after a couple of hours of use. This was troubling because my computer was loaded with 4GB of RAM and a 2.66 GHz i7 processor, so it should be plenty fast. Anyway, when I would notice my Mac running extremely slowly, I would generally exit all the apps I was running, and restart the computer. This would solve the problem temporarily, but after a couple more hours of use, my Mac would be running very slowly again.
I started investigating this and what I found was that if you have Mac OS X Snow Leopard or Lion, then Safari is most likely the reason why your system is running slowly. I discovered this by opening up Activity Monitor and finding that two processes, Safari and Safari Web Content, were hogging most of the CPU capacity, and the memory usage would climb significantly the longer you had Safari open.
Once I decided Safari was to blame, I did some Google searches on the topic and found that I was not alone. This thread on Apple’s support forum has hundreds of comments from users who have discovered the same thing. Some of the users note that keeping Gmail open in Safari makes the problem even worse.
Since I could not find a fix that would make Safari stop leaking memory and hogging processor power, I switched my default browser over to Google Chrome and my system is running lightning fast again. I will not be using Safari again until Apple fixes this.