putting an img tag inside of an a href tag causes a border around image in IE

I have some HTML where I have img tags inside of an href tag to use as a button. Everything works fine except that when I open it in IE, I get a border around the img tag.

Here's some code:

<a href="javascript:changecolor(1)" title="Click Again to Change Color" style="cursor:pointer; text-decoration:none"><img src="button.png" width="25" height="25" style="margin-top:600px;" /></a>
<a href="javascript:changecolor(2)" title="Click Again to Change Color" style="cursor:pointer"><img src="button.png" width="25" height="25" style="margin-top:600px;" /></a>
<a href="javascript:changecolor(3)" title="Click Again to Change Color" style="cursor:pointer"><img src="button.png" width="25" height="25" style="margin-top:600px;" /></a>
<a href="javascript:changecolor(4)" title="Click Again to Change Color" style="cursor:pointer"><img src="button.png" width="25" height="25" style="margin-top:600px;" /></a>
<a href="javascript:changecolor(7)" title="Click Again to Change Color" style="cursor:pointer"><img src="button.png" width="25" height="25" style="margin-top:600px;" /></a>
<a href="javascript:changecolor(6)" title="Click Again to Change Color" style="cursor:pointer"><img src="button.png" width="25" height="25" style="margin-top:600px; text-decoration:none" /></a>

How can I get rid of the blue border, which only appears in IE?