regarding the I1 equation:
if we go clockwise(as I1 flows) from the minus of the voltage sorse
first we go from minus to plus which gives us +Vr then we go threw 4ohm resistor which gives us +4I1 then we go threw a resistor where
we are going against I3 so its 4(I1-I3) and the same thing with thenext
resistor we get 4(I1-I2)

which gives us:+Vr+4I1+4(I1-I3)+4(I1-I2)=0

but if we look at the I1 equation here:
ImageShack - Hosting :: img8856io0.jpg

we got the opposite equation as if we multiplied by -1(which is fine)
except they kept +Vr as it is (i expected it will become -Vr)

why they kept it as +Vr??????????????