If you're not sure how to find out your own HL/CS SteamID please follow the steps below.Step 1: Connect to any Counter-Strike: Source server;
Step 2: Open your console (by default the ` key - otherwise check your control settings);
Step 3: Type
status into the console window;
Step 4: Your SteamID will be shown next to your nickname. It's the key with 'STEAM_'' in front;
Step 5: Enter that SteamID wherever needed (on your ESL, ED, UNGL profile or in your clan application)...
OR just use this website to find it: http://steamidchecker.com/