<script language="javascript">
var a="aaa <img   onMouseOver=this.style.cursor='pointer'   src='images/JoinContact.gif'   title='abcdff'> bbb"
alert(a)
alert(a.replace(/^.*? title=\'([^\']*?)\'.*?$/i,"$1"))
</script>

------解决方案--------------------
/title\s*=\s*[\s\S]+?(\'|\")/ig

------解决方案--------------------
把IMG加个ID

var title = getElementById("IMGID").getAttribute("title");