I'm newbie to Ubuntu and I'm using Ubuntu 14.04 (dual booted with Windows 7). Last few days it was working fine but from today my problem as follow as,

FIREFOX NOT WORKING IN UBUNTU

• Note: I had firefox only. Not anymore chrome etc...

Its says only,

SERVER NOT FOUND

But I don't see any network connecting problem in Windows 7

Note:

1. using Ethernet.

2. No proxey.

3. Manual method.

4. IPv4 settings.  

5. Wired connection.

update:

ip         -> 198.168.20.93   

netmask    -> 255.255.255.0   

gateway    ->198.168.20.14

dnsserver  ->198.168.20.14

How can I resolve my internet issue?

UPDATE 1:

ubuntu@P3-SD1:~$ ifconfig

eth0      Link encap:Ethernet  HWaddr 00:1c:c0:80:19:d3  

          inet addr:198.168.20.93  Bcast:198.168.20.255  Mask:255.255.255.0

          inet6 addr: fe80::21c:c0ff:fe80:19d3/64 Scope:Link

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:157600 errors:1865 dropped:2455 overruns:0 frame:1865

          TX packets:6437 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:12506428 (12.5 MB)  TX bytes:349342 (349.3 KB)



lo        Link encap:Local Loopback  

          inet addr:127.0.0.1  Mask:255.0.0.0

          inet6 addr: ::1/128 Scope:Host

          UP LOOPBACK RUNNING  MTU:65536  Metric:1

          RX packets:11260 errors:0 dropped:0 overruns:0 frame:0

          TX packets:11260 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:0 

          RX bytes:897196 (897.1 KB)  TX bytes:897196 (897.1 KB)

ubuntu@P3-SD1:~$ route -n

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

0.0.0.0         198.168.20.14   0.0.0.0         UG    0      0        0 eth0

198.168.20.0    0.0.0.0         255.255.255.0   U     1      0        0 eth0

ubuntu@P3-SD1:~$ cat /etc/resolv.conf

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)

#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

nameserver 127.0.1.1

ubuntu@P3-SD1:~$ ping www.google.com

ping: unknown host www.google.com

UPDATE 2:

ubuntu@P3-SD1:~$ cat /etc/network/interfaces

# interfaces(5) file used by ifup(8) and ifdown(8)

auto lo

iface lo inet loopback