Placeholders for Everyone

behavior.js

(function (w, d, a) {
  var $ = w[a.k] = {};
  $.a = a;
  $.w = w;
  $.d = d;
  $.f = (function () { 
    return {   
      focus: function (e) {
        var v = e || $.w.event, el = $.f.getEl(v), span = $.f.getPrev(el);
        if (span) {
          span.style.display = 'none';
        }
      },
      blur: function (e) {
        var v = e || $.w.event, el = $.f.getEl(v), span = $.f.getPrev(el);
        if (span && span.tagName === 'SPAN') {
          if (!el.value) {
            // field has no value; show label
            span.style.display = 'block';
          } else {
            // field has value; hide label
            span.style.display = 'none';
          }
        }
      },
      down: function (e) {
        var v = e || $.w.event, el = $.f.getEl(v);
        el.style.display = 'none';
        $.f.getNext(el).focus();
      },
      getEl: function (v) {
        var el;
        if (v.target) {
          el = (v.target.nodeType === 3) ? v.target.parentNode : v.target;
        }
        else {
          el = v.srcElement;
        } 
        return el;
      },
      getPrev : function (el) {
        var prevSib = el.previousSibling;
        if (prevSib && prevSib.nodeType !== 1) {
          prevSib = prevSib.previousSibling;
        }
        return prevSib;
      },
      getNext : function (el) {
        var nextSib = el.nextSibling;
        if (nextSib && nextSib.nodeType !== 1) {
          nextSib = nextSib.nextSibling;
        }
        return nextSib;
      },
      listen : function (el, ev, fn) {
        if(typeof $.w.addEventListener !== 'undefined') {
          el.addEventListener(ev, fn, false);
        } else if(typeof $.w.attachEvent !== 'undefined') {
          el.attachEvent('on' + ev, fn);
        }
      },  
      makePlaceholder : function (input, placeholder) {
        var span, rule;
        if (input.type === 'text' || input.type === 'password' ) {
          span = $.d.createElement('SPAN');
          span.innerHTML = placeholder;
          span.style.position = 'absolute';
          span.style.lineHeight = input.offsetHeight + 'px';
          for (rule in $.a.style) {
            if ($.a.style.hasOwnProperty(rule)) {
              span.style[rule] = $.a.style[rule];
            }
          }
          if (input.value) {
            span.style.display = 'none';
          }
          input.parentNode.insertBefore(span, input);
          $.f.listen(span, 'mousedown', $.f.down);
          $.f.listen(input, 'focus', $.f.focus);
          $.f.listen(input, 'blur', $.f.blur);
        }
      },
      init : function () {
        // no need to do any of this for browsers that understand placeholders
        if ($.d.createElement('INPUT').getAttribute('placeholder')) {
          return;
        }  
        var el, input, i, n, placeholder;
        input = $.d.getElementsByTagName('INPUT');
        for (i = 0, n = input.length; i < n; i = i + 1) {
          el = input[i];
          placeholder = el.getAttribute('placeholder');
          if (placeholder) {
            $.f.makePlaceholder(el, placeholder);
          }
        }
      }      
    };
  }());
  $.f.listen($.w, 'load', $.f.init);                                               
}(window, document, {'k': 'INPUT-PLACEHOLDERS', 'style': {'fontSize':'87%', 'marginLeft':'5px', 'color':'#aaa'}}));

structure.html

<p><input type="text" placeholder="username" value="foo" /></p>
<p><input type="password" placeholder="password1" /></p>
<p><input type="password" placeholder="password2" /></p>