Código PHP:
<form id="form1" name="form1" method="post" action="">
<input type="checkbox" name="checkbox" value="checkbox" onclick="this.checked=!this.checked" />
<input name="checkbox2" type="checkbox" value="checkbox" checked="checked" onclick="this.checked=!this.checked" />
<select name="select" onfocus="t=this.innerHTML;if(window.ActiveXObject)o=this.outerHTML;this.blur()" onchange="this.innerHTML=t;if(window.ActiveXObject)this.outerHTML=o">
<option>a</option>
<option selected="selected">b</option>
<option>c</option>
</select>
</form>
</