What is cron?
Cron is the name of a program that enables unix users to execute commands or scripts (groups of commands) automatically at a specified time/date.
We will be using cron to run a cleanup script on urX to ensure that old links are deleted and the shortening keys are refreshed for use with other links. The cleanup script that we will be using is called cron.php and it resides in your installation directory of urX. Each hosting company is different in the way they allow you to access the cron daemon so if you are unsure, email your administrator and find out.
For those of you that use cpanel, create a new cron and enter this string.
lynx -dump http://www.yourdomain.com/urx/cron.php > /dev/null
Basically, this allows cron.php to run and tells the daemon not to email you. Make sure you change the url to the url where you have urX installed.