From MozillaZine Knowledge Base
HTTP is the application-layer protocol with which most web pages are transferred. As part of the connection between client and server in HTTP 1.1, the client lists in what way it can/prefers to accept information (content negotiation). This preference controls which MIME types the application will report it supports.
Possible values and their effects
A comma-seperated list of MIME types with optional "q" (quality) values. A quality value says that the application prefers one type over another, but supports both. Quality values can be from 0 (not supported) to 1 (preferred format). If a quality value is omitted, it defaults to 1.
All others default:
Default in trunk builds after 2007-03-08:
First checked in
Has an effect in
- Netscape (all versions since 6.1)
- Mozilla Suite (all versions since 0.9.1)
- Phoenix (all versions)
- Firebird (all versions)
- Firefox (all versions)
- Thunderbird (all versions)
- Minimo (all versions)
- SeaMonkey (all versions)
- Bug 58040 - "Accept:" header should do something useful.
- Bug 170789 - HTTP Accept: header should be tailored to context of the request
- Bug 231357 - Remove universal image mimetypes from accept header
- Bug 240493 - HTTP Accept: header does not mention SVG
- Bug 309438 - Accept: header too long on account of text types
- Bug 361892 - bump application/xhtml+xml back to q=1.0 in the Accept: header when ready