I cant remember a game... I know that its an RPG... You were wizard... maybe it was something like 2D and there are alot of levels and you unlock new skills and things like that (RPG ) but Its one really really old game... (no its not multiplayer and its not a browser game)
More infos please,what you remind yet are part of so many RPGs.
Maybe you can squezze a few more informations out of your mind, like the setting, other classes (if they where others), monsters (special ones/bosses if possible), skills, dungeon crawler only or also under the free sky... we need defenetly more informations^^