fixnikon wrote:Many of the lens i (newb
ies) saw in internet and my fr
iend sa
id that other lens some cant autofocus on D40..?
Why Nikon not bu
ild some more opt
ion for D40.. i ask th
is because i want to find suitable and moderate cost of buy
ing themm

Only AF-S lenses will autofocus on the D40. Sigma has HSM lenses that should also work, but that's about it. The options are limited, and fairly pricey for the most part. The cheapest Nikon lenses besides the kit lens you can get are the Nikon 18-70, 18-135, and 55-200. After those, they go up drastically in price to ~$800 for the 18-200, $1000 and up for the likes of the 12-24 DX, 17-55 DX, 28-70, 80-200 AF-S, 300/4 AF-S, and the 70-200 VR.
Most of the Sigma lenses with HSM are telephotos and macros, excluding the 10-20 and 30/1.4