Whitespace around Image - css

Question

Can't figure out how I"m getting this extra white space around my image:
The markup:
<div id="member-name" hidden="true">
<button type="submit" id="btnExpandSection"><img src="~/Content/Images/plus.jpg" /></button><p id="member-fullName"></p>
</div>
the styles:
input, textarea
{
border: 1px solid #e2e2e2;
background: #fff;
color: #333;
font-size: .9em;
margin: 5px 0 6px 0;
padding: 5px 2px 5px 5px;
width: 300px;
}
img
{
display: block; /* gets rid off any unexpected margins round the image */
border: 0px;
}
input[type="submit"], input[type="button"], button
{
background-color: #ffffff;
cursor: pointer;
font-size: 11px;
font-weight: 600;
width: auto;
vertical-align: middle;
border: 0px;
}
td input[type="submit"], td input[type="button"], td button { font-size: 1em; }
UPDATE:
There's also this style in there:
#member-name
{
margin: 30px 0px 0px 0px;
height: 30px;
font-weight: bold;
color: white;
padding: 1px 1px 0px 1px;
background-color: #d28105;
border: 1px solid darkgray;
}
#member-fullName { margin: 0px 0px 0px 20px;}
#member-fullName p{ display: inline;float: left;overflow: hidden;}

Answer 1

Can't you just provide the image as a background to the button element?
#btnExpandSection {
background: #ffffff url('/Content/Images/plus.jpg') no-repeat center center;
height: /* image height */;
width: /* image width */;
}

Answer 2

I would start with this, and build it back from here...
button,
#member-fullName,
#member-name,
#btnExpandSection,
#btnExpandSection img {
margin: 0;
padding: 0;
}
But the following would definitely be preferably to an image nested between <button></button> tags. Replace 32px with actual width and height values of your image.
button {
background-image: url(~/Content/Images/plus.jpg);
width: 32px;
height: 32px;
}