Open web page link from command prompt

xdg-open http://google.com

dosen't work from RPI termainal

There's a command that knows about your default browser:

xdg-open http://google.com

This will also work for every other type of URI (Uniform Resource Identifier), like images - which will automatically open with eog, openoffice documents, and so on, and also on filesystem paths (xdg-open /tmp/foobar.png).

There is also

xdg-email team@stackexchange.com

and

xdg-mime query default text/html

To find out what application is going to be used.

You can set your preffered application by going to System → Preferences → Preferred Applications:

These utilities are part of the freedesktop.org specification, so you can use them in your applications - and it's going to work on all of the desktops that adhere to the spec.