Hi friends! 
I have got an Acer laptop. in one of the partion's I have got PC BSD installed. I am new UNIX user coz first I was using Windows, so I am still learning it. I only know few commands, and I find it very interesting.
Unfrtunately, when I log into PC BSD, I can't connect to the internet. 
What shall I do?
dubbio123
Not enough info to diagnose. What hardware do you have? Wireless or LAN? What kind? What version of PCBSD? Security settings? Have you tried the PCBSD forum? They have a "Knowledge Base" with a lot of that kind of stuff for newbies. Go to the command line and type "dmesg" and <enter> and you should be able to figure out what kind of hardware your system has on it. You can get more info about your LAN or wireless card by entering "ifconfig". That may get you started.
Tony
if you're running wireless and trying to connect to an unencrypted network, try this in your /etc/rc.conf
ifconfig_ath0="up"
you would replace ath0 with your detected wifi device (try dmesg |less for this) - you can try rebooting, or /etc/rc.d/netif restart to get it to latch on once you do this. for a WEP network, try (/etc/rc.conf again)
ifconfig_ath0="ssid SSID wepmode mixed weptxkey 1 wepkey KEY DHCP"
where SSID is, that's right, your ssid and KEY is your WEP key. use 0x at the beginning of the key for hex or nothing preceding for ascii.
to retry your device connection, try this simple script:
#!/bin/sh
rm /var/db/dhcli*lease*ath0
ifconfig ath0 down
ifconfig ath0 up
dhclient ath0
if these answers don't help, it's time to read the freebsd handbook. check out /usr/share/doc/en/books/handbook and look for the network-wireless chapter.
best of luck.
Thank you very much brother/sister. The information you gave is detailed. I will try to do so. Thank u again.