// wait for the DOM to be loaded
$(document).ready(function() {

    var ele_height = 0;

    function vertAlign(elem){

        var viewport = getVPSize();

        ele_height =  $(elem).height();

        var offset_y = Math.round((viewport[1] - ele_height) / 2);

        if(offset_y > 0){
            $(elem).css('margin-top', offset_y + "px");
        }

    }

    function getVPSize(){
        var doc_ele = document.documentElement;
        var vwidth = window.innerWidth || self.innerWidth || (doc_ele&&doc_ele.clientWidth) || document.body.clientWidth;
        var vheight = window.innerHeight || self.innerHeight || (doc_ele&&doc_ele.clientHeight) || document.body.clientHeight;
        arrayVPSize = [vwidth,vheight];
        return arrayVPSize;
    }

    vertAlign('#page_container')

    setInterval(function(){

        if(ele_height != $('#page_container').height()){
            vertAlign('#page_container')
        };

    }, 250);

});