Can one place a mosquito netting within 4 Tefachiim of the Sechach to prevent mosquitos and bees from entering. Is there any halacha problem. It lets in the sun and rain. Is it a Keli that is Mekabil Tumah? Any other issue to allow or prohibit use of it??? Is it different then Sadin of the Mishna?? Is it Allowed or just not approved of?

If the mosquito netting is within 4 handbreadths of the schach, there is no problem. Since it is clearly not in place of the schach (it lets in rain and sun) it would be clear for all to see that the purpose is protection from mosquitoes, so it cannot be construed as an alternate schach. Within 4 tephachim of the schach it is nullified in any case.