Also set the HTTP Vary header to indicate the dimensions of variance. Fiddling with Quality Values Apache sometimes changes the quality values from what would be expected by a strict interpretation of the Apache negotiation algorithm above. This is to get a better result from the algorithm for browsers which do not send full or accurate information. Some of the most popular browsers send Accept header information which would otherwise result in the selection of the wrong variant in many cases. If a browser sends full and correct information these fiddles will not be applied.
Some browsers routinely send wildcards in addition to explicit types they can handle.
The intention of this is to indicate that the explicitly listed types are preferred, but if a different representation is available, that is ok too. If some of the variants for a particular resource have a language attribute, and some do not, those variants with no language are given a very low language quality factor of 0.001. The reason for setting this language quality factor for variant with no language to a very low value is to allow for a default variant which can be supplied if none of the other variants match the browser's language preferences. The meaning of a variant with no language is that it is always acceptable to the browser. If the browser does not list either en or fr as acceptable, foo.html will be returned instead.