$(window).resize(function(){
page.style.height ="100%";
  var bodyheight = document.body.parentNode.clientHeight;
    if(bodyheight < 700 )
    {
        var bodyheight = document.body.parentNode.clientHeight;
    		expandToWindow(document.getElementById('page'));
    }
    else
    {
        expandToFull(document.getElementById('page'));
    }
});


$(document).ready(function() {
    var bodyheight = document.body.parentNode.clientHeight; 
    if(bodyheight < 700 )
        expandToWindow(document.getElementById('page'));
     
});

function expandToFull(element) {
    element.style.height ="100%";
}

function expandToWindow(element) {
    element.style.height = 700 + "px";
}