A couple years ago, before the arrival of Apple's innovative and groundbreaking iPhone, it used to make sense to have mobile versions of websites. Back then, bandwidth on mobile phones were limited and mobile browsers weren''t capable of displaying the full web.
I just installed a really useful FireFox addon: Tree Style Tab. It allows you to place your tabs on the top (default), left sidebar, right sidebar, or bottom. For me, it's the option to put the tabs on either sidebar that's most useful. My screen resolution is 1440. Since most websites have a max resolution of 1024, there's still a lot of space left for either sidebar.