Quality Value / Qvalue
Many HTTP request header fields use a
q parameter (case-insensitive) to assign a "weight" to a type of content. This weight is referred to as a "quality value" (or "qvalue"). The weight is a number in the range of
0.001 is the least preferred and
1 is the most preferred. A value of
0 means "not acceptable". If no
q parameter is present, the default weight is
1. A qvalue must not have more than three digits after the decimal point.