Shares in Caatoosee, the German online trading website creator, got off to a flying start on Wednesday as they debuted on Frankfurt's Neuer Markt, more than doubling in value as soon as trading began.

Dresdner Kleinwort Benson, which lead-managed the Caatoosee offering along with Landesbank Baden-Württemberg, on Tuesday priced the shares at €21 ($18), at the top of the indicated €18 to €21 range.