try
<a name="alink" href="www.abc.com">to abc</a><BR>
<input type="button" value="hide" onclick="document.getElementsByName('alink')[0].style.display='none';">
<input type="button" value="show" onclick="document.getElementsByName('alink')[0].style.display='';"><BR>
<input type="button" value="hide2" onclick="document.getElementsByName('alink')[0].style.visibility='hidden';">
<input type="button" value="show2" onclick="document.getElementsByName('alink')[0].style.visibility='visible';">