add a variable in appSteeing named whatever you want and set the value(left,right,middle).
now in the login div or in the outer div, whatever according to your design put an in line css with float or text-align with the value of <%=common.orientation %>
<div style="float:<%=common.orientation %>">
login form
</div>
and in web.config
<appSettings>
<add key="orientation" value="left" />
</appSettings>
Hope it will solve your problem.