basedialog = new DwtDialog(shell, null,"<b>Insert customer</b>", [DwtShell.CANCEL_BUTTON, DwtDialog.OK_BUTTON], null, null, DwtDialog.MODAL, null);
var html=["testing"].join("");
basedialog.setContent(html);
basedialog.popup();
I have manage to resolve this by myself. First off all you need a shell as your primary javascript object and then you just have to call popup function. Thaks for your noncooperation.

Joke. Now I have a different kind of problem. The buttons that substitute standardbuttons variable when I'm creating basedialog object are never in visible mode! Any clues?