function myPopupRelocate() {
 var scrolledX, scrolledY;
 if( self.pageYOffset ) {
   scrolledX = self.pageXOffset;
   scrolledY = self.pageYOffset;
 } else if( document.documentElement && document.documentElement.scrollTop ) {
   scrolledX = document.documentElement.scrollLeft;
   scrolledY = document.documentElement.scrollTop;
 } else if( document.body ) {
   scrolledX = document.body.scrollLeft;
   scrolledY = document.body.scrollTop;
 }

 var centerX, centerY;
 if( self.innerHeight ) {
   centerX = self.innerWidth;
   centerY = self.innerHeight;
 } else if( document.documentElement && document.documentElement.clientHeight ) {
   centerX = document.documentElement.clientWidth;
   centerY = document.documentElement.clientHeight;
 } else if( document.body ) {
   centerX = document.body.clientWidth;
   centerY = document.body.clientHeight;
 }

 var leftOffset = scrolledX + (centerX - 400) / 2;
 var topOffset = scrolledY + (centerY - 500) / 2;

 document.getElementById("mypopup").style.top = topOffset + "px";
 document.getElementById("mypopup").style.left = leftOffset + "px";
 document.getElementById("greyedout").style.top = scrolledY + "px";
 document.getElementById("greyedout").style.left = scrolledX + "px";
}


function fireMyPopup() {
 myPopupRelocate();
 document.getElementById("mypopup").style.display = "block";
 document.getElementById("greyedout").style.display = "block";
 document.body.onscroll = myPopupRelocate;
 window.onscroll = myPopupRelocate;
}

function urlencode( str ) {
    // http://kevin.vanzonneveld.net
    // +   original by: Philip Peterson
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +      input by: AJ
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // %          note: info on what encoding functions to use from: http://xkr.us/articles/javascript/encode-compare/
    // *     example 1: urlencode('Kevin van Zonneveld!');
    // *     returns 1: 'Kevin+van+Zonneveld%21'
    // *     example 2: urlencode('http://kevin.vanzonneveld.net/');
    // *     returns 2: 'http%3A%2F%2Fkevin.vanzonneveld.net%2F'
    // *     example 3: urlencode('http://www.google.nl/search?q=php.js&ie=utf-8&oe=utf-8&aq=t&rls=com.ubuntu:en-US:unofficial&client=firefox-a');
    // *     returns 3: 'http%3A%2F%2Fwww.google.nl%2Fsearch%3Fq%3Dphp.js%26ie%3Dutf-8%26oe%3Dutf-8%26aq%3Dt%26rls%3Dcom.ubuntu%3Aen-US%3Aunofficial%26client%3Dfirefox-a'
                                     
    var histogram = {}, histogram_r = {}, code = 0, tmp_arr = [];
    var ret = str.toString();
    
    var replacer = function(search, replace, str) {
        var tmp_arr = [];
        tmp_arr = str.split(search);
        return tmp_arr.join(replace);
    };
    
    // The histogram is identical to the one in urldecode.
    histogram['!']   = '%21';
    histogram['%20'] = '+';
    
    // Begin with encodeURIComponent, which most resembles PHP's encoding functions
    ret = encodeURIComponent(ret);
    
    for (search in histogram) {
        replace = histogram[search];
        ret = replacer(search, replace, ret) // Custom replace. No regexing
    }
    
    // Uppercase for full PHP compatibility
    return ret.replace(/(\%([a-z0-9]{2}))/g, function(full, m1, m2) {
        return "%"+m2.toUpperCase();
    });
    
    return ret;
}