Sources:
http://forums.battle.net/thread.html?topicId=27855845306&sid=3000http://classic.battle.net/diablo2exp/It’s that time again! On the morning of Tuesday, May 14, we’ll be conducting maintenance in order to reset the Diablo II ladder. We anticipate the realms could be down for up to six hours, and during that time all existing ladder characters will be converted to non-ladder. All characters and items being converted to non-ladder will remain intact, but once converted these characters will no longer have access to ladder content such as creating ladder-only rune words.
This ladder reset, like all those before it, creates a clean slate where all ladder characters begin at level 1 with no previous items to help them. To participate, simply wait until the Diablo II realms return to service on May, log in to Battle.net, and tick the “Ladder Character” checkbox when creating a new character. You can track ladder character leveling progress by clicking on the Ladder button from the main Diablo II in-game Battle.net interface.
For more information on ladder characters please visit the Arreat Summit at
http://classic.battle.net/diablo2exp/basics/charactertypes.shtml