Hi, How can i add a community , and pages in that community , need to modify the licalhost:8080/web/mycompany/login as default , instead of localhost:8080/web/guest/login

You can add community from liferay control panel by login with admin credentials.
Once you create the community , you can go to manage page section and can create public and private pages for that community.

Now you can change the friendly URL from community >> settings >> virtual host section where you can define page friendly URL and can give friendly URL of that community.

check this link

http://stackoverflow.com/questions/10498467/it-is-possible-to-create-a-custom-landing-page-in-liferay

Hi Shivaji,

You can get clified of all these from Documents provided by LIferay staff.

Please access this url http://docs.liferay.com/portal/5.2/official/ to get docs.

Thanks,
Anil S