Hack for IE8- on LAN doesn't try downloading s.gif

On LAN, a jsduck generated doc show missing s.gif image location
because IE8- browser try to download it on sencha.com site

I guess, it will work (works for my extjs applications) but I couldn't test it : I've can't succed in rake ext4 step (and I've had to modified <span>Chapter</span> in Chapter to pass previous rake step ...