Can I add an image to an ASP.NET button?
Although you can "replace" a button with an image using the following CSS...
.className { background: url(http://sstatic.net/so/img/logo.png) no-repeat 0 0; border: 0; height: 61px; width: 250px}...the best thing to do here is use an ImageButton control because it will allow you to use alternate text (for accessibility).
I actually prefer to use the html button form element and make it runat=server. The button element can hold other elements inside it. You can even add formatting inside it with span's or strong's. Here is an example:
<button id="BtnSave" runat="server"><img src="Images/save.png" />Save</button>