window.onload = init;
var d=document;
function init() {
  so_checkCanCreate();
}

function so_checkCanCreate() {
  // make sure the browser has images turned on. If they are, so_createCustomCheckBoxes will
  // fire when this small test image loads. otherwise, the user will get the hard-coded checkboxes
  testImage = d.body.appendChild(d.createElement("img"));

  // MSIE will cache the test image, causing it to not fire the onload event the next time the
  // page is hit. The parameter on the end will prevent this.
  testImage.src = "blank.gif?" + new Date().valueOf();
  testImage.id = "so_testImage";
  testImage.onload = so_createCustomCheckBoxes;
}

function so_createCustomCheckBoxes() {
  // bail out is this is an older browser
  if(!d.getElementById)return;
  // remove our test image from the DOM
  d.body.removeChild(d.getElementById("so_testImage"));
  // an array of applicable events that we'll need to carry over to our custom checkbox
  events = new Array("onfocus", "onblur", "onselect", "onchange", "onclick", "ondblclick", "onmousedown", "onmouseup", "onmouseover", "onmousemove", "onmouseout", "onkeypress", "onkeydown", "onkeyup");
  // a reference var to all the forms in the document

  frm = d.getElementsByTagName("form");
  // loop over the length of the forms in the document
  for(i=0;i<frm.length;i++) {
    // reference to the elements of the form
    c = frm[i].elements;
    // loop over the length of those elements
    for(j=0;j<c.length;j++) {
      // if this element is a checkbox, do our thing

      if(c[j].getAttribute("type") == "checkbox") {
        // hide the original checkbox
        c[j].style.position = "absolute";
        c[j].style.left = "-9000px";
        // create the replacement image
        n = d.createElement("img");
        n.setAttribute("class","chk");
        // check if the corresponding checkbox is checked or not. set the
        // status of the image accordingly
        if(c[j].checked == false) {
          n.setAttribute("src","check0.gif");
          n.setAttribute("title","click here to select this option.");
          n.setAttribute("alt","click here to select this option.");
        } else {
          n.setAttribute("src","check1.gif");
          n.setAttribute("title","click here to deselect this option.");
          n.setAttribute("alt","click here to deselect this option.");
        }
        // there are several pieces of data we'll need to know later.
        // assign them as attributes of the image we've created
        // first - the name of the corresponding checkbox
        n.xid = c[j].getAttribute("name");
        // next, the index of the FORM element so we'll know which form object to access later

        n.frmIndex = i;
        // assign the onclick event to the image
        n.onclick = function() { so_toggleCheckBox(this,0);return false; }
        // insert the image into the DOM
        c[j].parentNode.insertBefore(n,c[j].nextSibling)
        // this attribute is a bit of a hack - we need to know in the event of a label click (for browsers that support it)
        // which image we need turn on or off. So, we set the image as an attribute!
        c[j].objRef = n;
        // assign the checkbox objects event handlers to its replacement image
        for(e=0;e<events.length;e++) if(eval('c[j].' +events[e])) eval('n.' + events[e] + '= c[j].' + events[e]);
        // append our onchange event handler to any existing ones.
        fn = c[j].onchange;
        if(typeof(fn) == "function") {
          c[j].onchange = function() { fn(); so_toggleCheckBox(this.objRef,1); return false; }
        } else {
          c[j].onchange = function () { so_toggleCheckBox(this.objRef,1); return false; }
        }
      }
    }
  }
}

function so_toggleCheckBox(imgObj,caller) {
  // if caller is 1, this method has been called from the onchange event of the checkbox, which means
  // the user has clicked the label element. Dont change the checked status of the checkbox in this instance
  // or we'll set it to the opposite of what the user wants. caller is 0 if coming from the onclick event of the image
  
  // reference to the form object
  formObj = d.forms[imgObj.frmIndex];
  // the name of the checkbox we're changing
  objName = imgObj.xid;
  // change the checked status of the checkbox if coming from the onclick of the image
  if(!caller)formObj.elements[objName].checked = !formObj.elements[objName].checked?true:false;
  // finally, update the image to reflect the current state of the checkbox.
  if(imgObj.src.indexOf("check1.gif")>-1) {
    imgObj.setAttribute("src","check0.gif");
    imgObj.setAttribute("title","click here to select this option.");
    imgObj.setAttribute("alt","click here to select this option.");
  } else {
    imgObj.setAttribute("src","check1.gif");
    imgObj.setAttribute("title","click here to deselect this option.");
    imgObj.setAttribute("alt","click here to deselect this option.");
  }
}