Running xserver on vps/dedicated server

Use Xvfb on ubuntu/debian it is in package xvfb

used in this manner

Xvfb :1 &
env DISPLAY=:1 firefox
DISPLAY=:1 firefox
ssh -t -L 5900:localhost:5900 far-away.east 'x11vnc -localhost -display :0'
xtightvncviewer -encodings "copyrect tight hextile" localhost:0
ssh -t -L 5900:localhost:5900 server 'x11vnc -localhost -display :1'

Also simpler is you use
xvfb-run python testjs.py