URL Related Information

document.referrer: '' Where the visitor has come from.
self.location: '' URL of this page.
top.location: '' Different if page is framed.

Browser Information

navigator.appName: '' Typically one of 'Microsoft Internet Explorer' or 'Netscape'.
document.images: Undefined if browser does not support images.
document.layers: Undefined if browser does not support layers.
document.all: Undefined if browser does not support DHTML.
document.frames: Undefined if browser does not support frames.
navigator.systemLanguage: For a list of possible codes see http://msdn.microsoft.com/library/default.asp?url=/workshop/author/dhtml/reference/language_codes.asp.

Probably Internet Explorer only.
navigator.userLanguage:

Screen Information

screen.availHeight:  
screen.availWidth:  
screen.height:  
screen.width:  
screen.pixelDepth:  
screen.colorDepth:  

Window Information

window.outerWidth:  
window.outerHeight:  
window.innerWidth:  
window.innerHeight:  
document.body.clientWidth: Equivalent to window.outerWidth.
document.body.clientHeight: Equivalent to window.outerHeight.