This is copied from FireBug, notice the missing class for the Login Button but the Register Button has a class.
<tr>
<td width="50%" align="right" runat="server" id="TDLogin">
<input type="submit" id="btnLogin_964" onclick="Javascript:__doPostBack('UserLogin','');"
value="Login" name="btnLogin_964">
td>
<td width="50%" align="left" runat="server" id="TDRegister">
<input type="submit" class="DynamicLogin_RegisterButton" id="btnRegister_964"
onclick="Javascript:__doPostBack('UserRegistration','');" value="Register" name="btnRegister_964">
td>tr>