To create the DHTML pop up menu you should set the following parameter:

var popupMode=1;

Then appoint code in the following format to the event you want:

return dm_popup(menuInd, pause, event, x, y)

menuInd - index of the menu on a page, >= 0.
pause - sets the time when the menu will be hidden.
event - constant. Do not change.
x, y - optional. You should set these parameters when you want to show the menu in the specific place. In other case the dhtml will be shown in the mouse position.

For example:
     <img src="mypic.gif" onClick="return dm_popup(0, 1000, event);">
     <input type=button value="Show Menu" onClick="return dm_popup(1, 2000, event, 100, 50);">