I had an interesting problem with one of the sites I tried loading a while ago. weibo.com was using jQuery (version 1.7.2) which tries to detect browser features, and decided Flow was actually Internet Explorer. It later tried to use IE-specific filters rather than CSS opacity, so no fades worked. I tracked this down to jQuery's startup code setting opacity to 0.55 and then getting it back out again. Since we converted 0.55 into 16.16 fixed point too early, it was retrieving it as 0.549988. That wasn't equal to 0.55, and so jQuery decided Flow didn't support opacity and therefore must be Internet Explorer.
Browsers use fixed point maths internally for storing the results of many calculations. Often 26.6 bits, which gives 64 positions between (CSS) pixels, or 24.8 bits to give 256 levels of anti-aliasing in graphics.
Our initial design for CSS style tried to use the most applicable value possible, so for the width property we would store the parsed value as 26.6 precision but SVG values would often use 16.16 precision (the SVG Tiny 1.2 spec suggests this).