i was playing a bit with the national's webench tool, and i want some info from this circuit if there is any practicular things to watch out when i lay it out and make the prototype for the first time from this, i hope i calculated right the dynamic resistance of the led according to the example from the national site, however i noticed its gave line frequency 60Hz but im not in the US so here the mains frequency is 50Hz but of course it will be rectified and filtered before it reaches the pcb. files are in the included zip. thanks for all of you who give me a reply