IE adds input margin / padding

[unemployment]

How can I make this button cross browser compatible?  IE7 is rendering the input padding, some how even though it is set to 0.

 

input { width:auto;
overflow:visible; }
input.invis[type="submit"], input.invis[type="button"]{
background: transparent none no-repeat 0 0 scroll;
border: 0px none;
-moz-box-shadow: none;
box-shadow: none;
text-shadow: none;
padding: 0;
margin: 0;
color: inherit;
font-size: 14px;
}
span.button.invis{
background: transparent none no-repeat 0 0 scroll;
border: 0px none;
-moz-box-shadow: none;
box-shadow: none;
text-shadow: none;
padding: 0;
margin: 0;
color: inherit;
font-size: 14px;
}
span.button.invis a{
font-size: 10px;
margin: 5px 3px 0 0;
padding: 3px;
border: 1px solid transparent;
}
span.button.invis a:hover{
font-size: 10px;
margin: 5px 3px 0 0;
padding: 3px;
-moz-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.1);
box-shadow: 0 1px 0 rgba(0, 0, 0, 0.1);
    background: #fff;
    border-color: #999999 #999999 #888888;
    border-style: solid;
    border-width: 1px;
    line-height: normal !important;
    text-align: center;
    text-decoration: none;
    vertical-align: top;
    white-space: nowrap;
}
.button{
-moz-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.1);
box-shadow: 0 1px 0 rgba(0, 0, 0, 0.1);
    background: #fff;
    border-color: #999999 #999999 #888888;
    border-style: solid;
    border-width: 1px;
    font-size: 11px;
    margin: 0px 3px;
padding: 4px 8px;
    text-align: center;
    text-decoration: none;
    white-space: nowrap;
float: left;
}
.dark_grey{
color: #333333 !important;
}
.button:hover, .button label:hover{
cursor: pointer;
}
.button a{
font-size: 14px;
font-weight: bold;
font-family:Helvetica Neue,Helvetica,Arial;   
}
.button.disabled{
opacity:0.4;
filter:alpha(opacity=40)
}
.button label{
padding: 0;
margin: 0;
}
<fieldset class="mvs plm buttonfield">
<input type="hidden" name="action" id="action" value="" />
	<span class="button">
		<label>
			<input type="button" id="starttop" class="invis dark_grey" value="New Conversation" />
                         </label>
	</span>
	<span id="smarktop" class="button disabled">
		  <label>
			  <input type="button" id="marktop" class="invis dark_grey" value="Mark as Read" disabled="disabled" />
		  </label>
	</span>
	<span id="sdeletetop" class="button disabled">
		  <label>
                                   <input type="button" id="deletetop" class="invis dark_grey" value="Delete" disabled="disabled" />
		  </label>
	</span>
</fieldset>