function alignDivs() {
   var mainDiv = document.getElementById("main");
   var winHeight = 0;
   if( typeof( window.innerWidth ) == 'number' ) {
      //Non-IE
      winHeight = window.innerHeight;
   } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
      //IE 6+ in 'standards compliant mode'
      winHeight = document.documentElement.clientHeight;
   } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
      //IE 4 compatible
      winHeight = document.body.clientHeight;
   }
//   window.alert( 'Height = ' + winHeight );
    var newHeight = winHeight
        - document.getElementById("top").offsetHeight
        - document.getElementById("top_menu").offsetHeight
        - document.getElementById("main_top").offsetHeight
        - document.getElementById("footer").offsetHeight
        - document.getElementById("authors").offsetHeight
        + 16;
    mainDiv.style.minHeight = newHeight + 'px';
}