I wanted this in IE, but I couldn't find a plugin that did it. All the other gestures plugins I've seen have done the more complicated "hold down a button and wiggle the mouse a certain way" gestures.
So AHK to the rescue:
#IfWinActive ahk_class IEFrame RButton & LButton::Send, !{Left} RButton up::Send, {RButton} LButton & RButton::Send, !{Right} LButton up::Send, {LButton} #IfwinActive