How to make Xvfb display visible?

I am running selenium through Xvfb on display number :99 like this:

/usr/bin/Xvfb :99 -ac -screen 0 1024x768x8 & export DISPLAY=":99" && \
java -jar /usr/lib/selenium/selenium-server-standalone-2.24.1.jar -port 4444

However display with number other than :0 is not visible by default. How do I make it visible to actually see what selenium is doing in the browser?