Problem with image on button in IE

Code:
<td><input type='button' id='btnStyle' align='centre' value=''/></td>

#btnStyle
{
width:15px;
height:20px;
font-size:6px;
font-family: 'arial';
background:url(../images/edit.gif);
}

These work fine in all browser, the button is displayed with the correct image but in IE8 the buttons are half the width, and at the same time image is also not visible on it Can anyone help?

The "auto" might cause Internet Explorer to view the images in their full size.Try this code

Code:

.btnStyle
{
width: auto;
height: auto;
font-size: 9px;
font-family: 'Tahoma';
background: url("../images/edit.gif");
}