Create a file: /usr/share/X11/xorg.conf.d/synaptics.conf

In that file put..

Section "InputClass"
     Identifier "Touchpad" # required
     MatchIsTouchpad "yes" # required
     Driver "synaptics" # required
     Option "MinSpeed" "0.5"
     Option "MaxSpeed" "1.0"
     Option "AccelFactor" "0.075"
     Option "TapButton1" "1"
     Option "TapButton2" "2" # multitouch
     Option "TapButton3" "3" # multitouch
     Option "VertTwoFingerScroll" "1" # multitouch
     Option "HorizTwoFingerScroll" "1" # multitouch
     Option "VertEdgeScroll" "1"
     Option "CoastingSpeed" "8"
     Option "CornerCoasting" "1"
     Option "CircularScrolling" "1"
     Option "CircScrollTrigger" "7"
     Option "EdgeMotionUseAlways" "1"
     Option "LBCornerButton" "8" # browser "back" btn
     Option "RBCornerButton" "9" # browser "forward" btn
EndSection

Restart XServer