Help needed with a parser error

Hi all,
I'm really struggling to pinpoint a problem that I'm having with a button tag.  No matter what I try, I get the same error message every time:
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: The server tag is not well formed.

Source Error:
Line 64: <tr>
Line 65: <td width="100%" colspan="3">
Line 66: <asp:Button id="btnSubmitContact" CSSClass"buttonstyle" CommandName="ButtonContact_Click" runat="server"/>
Line 67: </td>
Line 68: </tr> 
 
No matter what I do, I keep getting this error.  ...