Can't Connect To Internet In Linux

This means the eth0 couldnt get any ip address.
Do you have a DHCP server on the LAN ?

or you can do one thing.. have a static IP for the eth0 (assuming eth0 is the network card hooked on to your LAN). Open '/etc/network/interfaces'

and have something like this...

======
# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

# The loopback interface
auto lo
iface lo inet loopback

# The first network card - this entry was created during the Debian installation
# (network, broadcast and gateway are optional)

auto eth0
iface eth0 inet static
address 192.168.0.50
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255
gateway 192.168.0.10
======

Remove all the other interfaces ie. eth1, eth2... till wlan0..
Now check...