I own an ASUS EEE PC 904 HD and ASUS.com says it supports 802.11 b/g. I was going to buy a D-Link DIR-615 WLAN Router, but I read it uses 802.11n ! So, will my ASUS EEE be able to connect to this network?
Another question if I may, how good range of connectivity do you think that router has?
Yes, Wireless N is basically backward-compatible; N adapters can connect to b/g routers and N routers can accept b/g WiFi devices. Of course, in either case, you won't reach the speeds promised by the N standard.
Regarding the range of connectivity, you will definitely notice a range increase if you're switching from a G router. To be safe though, take what's marketed by D-Link and halve the values.