How can i transfer values from one window to another (parent to child) in a browser

I have a html page with One link. When the user clicks on the link a new window gets opened with another site (another domain) which have two textboxes, these textboxes should be populated with the values present in the parent window, so the the user does not have to enter it again.  I wrote a javascript function

function openWindow(){
    var _newWin = window.open("http://www.anotherDomain.com","_newWin");
    var firstName = _newWin.document.getElementById("firstTextBoxID");
    firstName.value = "New Value";
}

Nothing is happening, is this because of some security reasons or we cannot communicate cross domain.