JS控制下拉菜单框，动态改变图片

<select id="s1" onchange='document.getElementById("pic").src=this.value'>
<option value="http://bbs.blueidea.com/images/smilies/default/biggrin.gif">biggrin</option>
<option value="http://bbs.blueidea.com/images/smilies/default/confused.gif">confused</option>
<option value="http://bbs.blueidea.com/images/smilies/default/cool.gif">cool</option>
<option value="http://bbs.blueidea.com/images/smilies/default/eek.gif">eek</option>
<option value="http://bbs.blueidea.com/images/smilies/default/frown.gif">frown</option>
<option value="http://bbs.blueidea.com/images/smilies/default/han.gif">han</option>
<option value="http://bbs.blueidea.com/images/smilies/default/mad.gif">mad</option>
<option value="http://bbs.blueidea.com/images/smilies/default/redface.gif">redface</option>
<option value="http://bbs.blueidea.com/images/smilies/default/rolleyes.gif">rolleyes</option>
<option value="http://bbs.blueidea.com/images/smilies/default/smile.gif">smile</option>
<option value="http://bbs.blueidea.com/images/smilies/default/tongue.gif">tongue</option>
<option value="http://bbs.blueidea.com/images/smilies/default/wink.gif">wink</option>
</select>
<img id="pic" src="http://bbs.blueidea.com/images/smilies/default/biggrin.gif" border="0" width="15">