I have been running a small experiment recently. Namely, I rlimit'ed the browser to use just 512 MiB of RAM by
$ bash -c "ulimit -m 512000 && firefox"

and then observed the following scenario:
Chromium consumed about 300 MiB of memory in a matter of minutes and then continued to grow until it segfaulted.
Firefox 26 consumed just 150 MiB, but regardless it will segfault within 2 hour time.

What I am searching is a HTML5 capable browser, that does not consume so much freaking ram. No more than 512 MiB dedicated to browser would be optimal. I do not use Adobe Flash.

I know that page render consumes a lot of resources, but I mostly work with 5-6 tabs open and the rest of 10-15 tabs is passive and opened only when I need them.