<div id="mainDIV">...</div>
<script>


modalWindow = null;
wndTitle = ':: ';

function showModalWindow(handle, title, w, h, html) {

    var win = document.createElement('div');
    var time = (new Date).getTime();
    win.style.position = 'absolute';
    win.style.width = w;
    win.style.height = h;
    win.style.backgroundColor = '#f5f5f5';
    win.style.border = '1px solid #a0a0a0';
    win.style.paddingTop = '2px';
    win.style.left = '300px';
    win.style.top = '300px';
    win.style.filter= 'alpha(opacity=20)';
    win.style.opacity='56';
    win.id = 'dmainWindow'+time;
    win.style.zIndex = time;

    win.onclick = function() {

        with(this) { style.zIndex = (new Date).getTime(); }

    }

    iHTML = '<div class="windowBar" onmousedown="return setDnD(event,this,\'dmainWindow'+time+'\');">';
    iHTML += ' &nbsp; '+wndTitle+' '+title;
    iHTML += '</div>';
    iHTML += '<div class="closeButton" onclick="this.parentNode.style.display = \'none\'; this.parentNode.style.visibility = \'hidden\'; this.parentNode.innerHTML = null; modalWindow = null;">';
    iHTML += 'X';
    iHTML += '</div><br />';
    iHTML += '<div style="padding: 5px;">'+html+'</div>';

    win.innerHTML = iHTML;

    //handle.parentNode.insertBefore(win,handle);
    //document.body.appendChild(win);
    document.getElementById('mainDIV').appendChild(win);

    /*
    var winBar = document.createElement('div');
    winBar.style.cursor = 'pointer';
    winBar.style.backgroundColor = '#b70000';
    winBar.style.color = '#ffffff';
    winBar.style.fontSize = '10px';
    winBar.style.fontFamily = 'tahoma';

    winBar.innerHTML = 'AQQ';

    win.parentNode.insertBefore(winBar,win);
    */

    modalWindow = win;

    var winForm = win.getElementsByTagName('form');
    winForm[0].onsubmit = function (){
        with(this) {

        var out = '-';

            for(var a=0; a<elements.length; a++) {

              //if (elements[a].type != 'submit') {
                out += "&"+elements[a].name+'='+elements[a].value;
              //}

            }

        }

        out = out.replace('-&', '');
        out = out.replace('-', '');

         win.style.display = 'none';
         win.style.visibility = 'hidden';
         win.innerHTML = null;
         modalWindow = null;

        //test = out;

        // if (handle) {
             handle.innerHTML = out;
             handle.value = out;
             return out;
        // } else {
             //return "b";
         //}
    }

}

window.onload = function () {
	var htmlCode = '<form><input type=submit name=hm value=tak /> <input type=submit value=nie /></form>';
	var test = showModalWindow(this, 'test2', 230, 100, htmlCode);
}
</script>
<div id="mainDIV">
	ugh
</div>
<a href="javascript:void(0);" onclick="alert(test);">TEST</a>