These are permalinks. They cannot be edited in any way, as these urls are unique to each user. Use http://steamidconverter.com to make sure you're not trading with an impersonator.

Main account: http://steamcommunity.com/profiles/76561198038408943

Alt account 1: http://steamcommunity.com/profiles/76561198065194190/
Alt account 2: http://steamcommunity.com/profiles/76561198072465572/
Alt account 3: http://steamcommunity.com/profiles/76561198073054464/
Alt account 4: http://steamcommunity.com/profiles/76561198072306373/

Other tips:
-Make sure the url is /profiles/76561198038408943 and NOT /user/76561198038408943
-My main account's profile will never be private or friends-only
-If you're still confused, you can use the link on my youtube channel which redirects to my profile