ECMAScript (DOM)

<script>
function get_root(el) {
  while (el && el.parentNode) { el = el.parentNode; }; 
  return el;
}
</script>

<a id="MY_A_TAG" href="javascript:alert(this)"
   onclick="alert(get_root(document.getElementById('MY_A_TAG')))">
   zeige an 
</a>

<style>
.center { display: block; text-align: center; }
.blau   { background-color: #009; color: #fff; }
.border { border: 1px solid #ccc; }
.w100  { float: left; width: 100px; margin: 0 1px; }
.clear  { clear: both; }
</style>

<div class="center">
  <a class="w100 blau border" href="#"
     onclick="alert('Button 1');"> Button 1
  </a>
  <a class="w100 blau border" href="javascript:alert('href');"
     onclick="alert('Button 2'); return false;"> Button 2
  </a>
  <a class="w100 blau border" href="javascript:void(0);"
     onclick="alert('Button 3');"> Button 3
  </a>
</div><br class="clear" />

<style>
.button { display: inline; text-decoration: none;
 font-size: 80%;     border-width: 3px;    
 font-style: normal; border-style: outset;
 color: #fff;        background-color: #99a;
 padding: 0px 4px;   margin: 0px 4px; 
}
a                { background-color: #999;}
a.button:link    { background-color: #999;}
a.button:visited { background-color: #999;}
a.button:hover   { background-color: #ccc;}
a.button:active  { background-color: #999;}
</style>

<a class="button"
   href="javascript:alert('Button1-Test')"> Button1
</a>

<a class="button" href="javascript:alert('Button2-Test')"
   onmouseover = "this.style.backgroundColor='#ccc';"
   onmouseout  = "this.style.backgroundColor='#f00';"
   onmousedown = "this.style.backgroundColor='#00f';"
   onclick     = "this.style.backgroundColor='#0f0'; return false;">
   Button2
</a>

<script>
function get_style(that, ev, cssprop){ 
  var doc = document, style, 
      ev = ev || window.event; /* 1 */ 

  if (doc.defaultView && doc.defaultView.getComputedStyle) { 
    style = doc.defaultView.getComputedStyle(that, null);
  } else { //IE < 9
    style = that.currentStyle || that.style;
  } 
  return style[cssprop] || style.getPropertyValue(cssprop);
}
</script>

<a href="javascript:alert('Button-Test')"
   onmouseover = "this.style.backgroundColor='#f00';"
   onmouseout  = "this.style.backgroundColor='#0f0';"
   onmousedown = "this.style.backgroundColor='#00f';"
   onclick     = "alert(get_style(this,event,'backgroundColor'));return true"> 
   Button
</a>

<div id="mydom"> <b>Hallo</b> <i>Welt</i> </div>
<script>
var win = window, doc = win.document;

var s="", br = " ", child, par = doc.getElementById('mydom');
for (child = par.firstChild; child; child = child.nextSibling) {
  s += child.nodeName + br;
} doc.write(s);
</script>

<div id="myid" title="hallo welt" ></div>
<script>
  var id = "myid",
  el = document.getElementById(id) || {innerHTML:''};
  el.innerHTML = el.title || 'zugriffsfehler';
  if (!el.nodeName) { alert(el.innerHTML); }
</script>

<div id="my_id" title="nachher">vorher</div>
<script>
 var el, id = " my_id";
 try{
   el = document.getElementById(id);
   el.innerHTML = el.title || 'zugriffsfehler';
 } catch(e) {
   alert(e);
 }
</script>

<img name="meineVornamen" ... />
<img name="Walter Manfed" ... />
<script>
var img = window.document.images, sav = { }, name, i, erg;
for (i = 0; i < img.length; i += 1 ) {
  name = img[i].name;
  if ( name && name.length > 0 ) { 
    sav.name = i; /** 1 **/
  } 
}
erg = sav.meineVornamen + ' ';
erg += sav['Walter Manfed']; alert(erg);
</script>

<img name="meineVornamen" ... />
<img name="Walter Manfed" ... />
<script>
var img = window.document.images, sav = { }, name, i,erg;

for (i = 0; i < img.length; i += 1 ) {
  name = img[i].name;
  if ( name && name.length > 0 ) { 
    sav[name] = i; /** 1 **/
  } 
}
erg = sav.meineVornamen;
erg += ' ';
erg += sav['Walter Manfed']; alert(erg);
</script>