Move a line

<style type="text/css">
                .line
        {
                        position: absolute;
                        height: 0px;
                border-width: 2px 0px 0px 0px;
                border-style: solid;
                border-color: #99aadd;
                }
</style>
<script type="text/javascript">
                var isIE = navigator.userAgent.indexOf("MSIE") > -1;
                window.onload = init;
                function createLine(x1, y1, x2, y2)
        {
                if (x2 < x1)
                {
                        var temp = x1;
                                x1 = x2;
                                        x2 = temp;
                                temp = y1;
                                        y1 = y2;
                                y2 = temp;
                        }
                        var line = document.createElement("div");
                        line.className = "line";
                        var length = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
                        line.style.width = length + "px";
                                if (isIE)
                        {
                                line.style.top = (y2 > y1) ? y1 + "px" : y2 + "px";
                                line.style.left = x1 + "px";
                                var nCos = (x2-x1)/length;
                                        var nSin = (y2-y1)/length;
                                        line.style.filter = "progid:DXImageTransform.Microsoft.Matrix(sizingMethod='auto expand', M11=" + nCos + ", M12=" + -1*nSin + ", M21=" + nSin + ", M22=" + nCos + ")";
                                }
                                else
                                {
                                        var angle = Math.atan((y2-y1)/(x2-x1));
                                        line.style.top = y1 + 0.5*length*Math.sin(angle) + "px";
                                        line.style.left = x1 - 0.5*length*(1 - Math.cos(angle)) + "px";
                                        line.style.MozTransform = line.style.WebkitTransform = line.style.OTransform= "rotate(" + angle + "rad)";
                                }
                                return line;
                        }

                        function init()
                        {
                                var demoElement = document.getElementById("demo");
                                demoElement.appendChild(createLine(0, 0, 100, 0));
                        }
                        function change()
                        {
                                var demoElement = document.getElementById("demo");
                                demoElement.removeChild(demoElement.childNodes[0]);
                                demoElement.appendChild(createLine(200, 200, 100, 100));

                        }
                </script>
  <div id="demo"></div>
<input type ="button" onclick="change();" />