Nope; if it's px-based, it's not fluid by definition. Fluid is when you use em or % to define width (or height). The possible caveat for px is for min-width if you don't want your elements to shrink beyond a certain size (which totally defeats the purpose for resolutions smaller than your min-width. I'd call layouts with unreasonable min-widths [say, greater than 240] semi-fluid). Your link is a great example:it is fluid for screens between 720 and 1280px, but fixed beyond those bounds
I did a google search for "Fluid layout" and this link was directly above the one you provided http://coding.smashingmagazine.... You might notice the lack of px's