ProServe will be moving it's colocation servers to another datacenter tonight, including the one where WhatPulse runs on.
The move will start at 19:00 GMT, and could last a maximum of 6 hours. (usually it's around 3 hours). So there is a chance you won't be able to pulse or visit the website during that time.
After the server has arrived at the new datacenter, everything will start to run again, and you will be able to pulse again.