Assuming that by 'call' you mean 'open in a web browser' then you can do as TobiSGD suggested, or use a variant on that
$ xdg-open http://your.url.here
$ x-www-browser http://your.url.here
should open the url in the user's default web browser. (Where default is as set via whatever preferences are available for that. E.g. in GNOME there's gnome-default-applications-properties which you can get by typing that at a command prompt or will be available in the Control Centre or Preferences or whatever Linux distro it is that you are using (which you should add to your profile or state in your post) calls them as Preferred Applications.