Depends on the site and client. Some fixed, some liquid. I prefer liquid though because I find it tends to look nicer and issues of screen resolution and size are minimized.
I prefer liquid, but liquid can't usually be done for many flashy or completely image based websites. Then again, i don't like bloated websites that are fixed anyway.
it is always better to design sites to fit all screen resoltions.
because websites usually get visitors from around the world.
and they may be using different screen resolutions.
if we design for small screen, that will look too small in larger screens.
if we design for large ones, that requires scrolling in small screens.
use % for heights and widths.
