Well, the wonderful Valve has decided to COMPLETELY CHANGE THEIR UUID (Unique User Identification) system, you probably know as a "SteamID". Now, we will be using our "Unique IDs", which look like this: [U:1:100345391]. Nasty, I know. However, we are going to have to use this from now on. The ONLY possible good thing about this, is that this could be changed in preparation for Source2.

How To Get Your Unique ID:

There are currently no sites (such as steamrep or steamidfinder) that can provide you your Unique ID. To get your ID, join any server, and type "status" into the Dev Console. Look for your name on the list and write down your ID.