http://steamcommunity.com/id/<steamID>/
e.g. http://steamcommunity.com/id/your_steamid/
or
http://steamcommunity.com/profiles/<steamID64>/  ^{(17 digits)}
e.g. http://steamcommunity.com/profiles/12345678912345678/

1. Your Steamprofile must be Public!
2. for steamID you have to set a custom URL!
3. you can find your steamID64 here