HTTP headers "q" factor in firefox?

Question

Does anyone know what the "q" factor HTTP headers emitted by Firefox 3 mean?

It only appears in the Accept and Accept-Charset headers.

For example:

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,****/****;q=0.8

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

I've tried trawling the web but I haven't quite found the answer.

Is it some sort of weighting, heuristic value or something to do with localization?

Thanks,

Phil'

Answer 1

This page should clarify the "q" parameter, which comes from "quality factor".

Quality factors allow the user or user agent to indicate the relative degree of preference for that media-range, using the qvalue scale from 0 to 1. The default value is q=1.