<a href="#" onclick="aa()">test1</a>
<a href="javascript:void(0)" onclick="aa()">test2</a>
<a href="www.baidu.com" onclick="aa(),return false"></a>
<a href="javascript:void(0)" onclick="aa()">test2</a>
<a href="www.baidu.com" onclick="aa(),return false"></a>