Safari and chrome being slow
HEy I have recently bought a mac book pro, about two weeks ago and it has had problems loading certain webpages, the website "the verge" and "cnet" seem to give it trouble, I'm not sure if they are just not made to run on a Mac or what. So I called apple and they had me reset my computer and reinstall the os and it didn't seem to help, I am starting to think it is just the websites fault. Does anyone Else have trouble with those cites?? And I am a bit worried about reinstalling my os, I already did it but apple care didn't have me erase anything I just hit "command r" while the laptop was powering up and hit reinstall OS X. Can reinstalling an os like that slow your computer down any?? I'm new to macs sorry.
OS X Yosemite (10.10.4)