From MozillaZine Knowledge Base
RFC 3987 describes how IRIs (Internationalized Resource Identifiers) work. Mozilla implements IRIs in part by allowing IRIs to be converted to URIs. However, many websites break with this option enabled.
For compatibility with these websites, as well as parity with IE and Opera, Mozilla now treats the query portion of a URI (the part following the
Possible values and their effects
Encode the query portion of IRIs as UTF-8.
Encode the query portion of IRIs using the same encoding as the current page. (Default)
If you commonly use websites that use “extended” (non-ASCII) characters in their URIs, you should probably leave this preference as false.
First checked in
Has an effect in