What I’m seeing, in Chrome, is a left-margin between the 800px and 560px breaks, but below 560px the left-margin disappears.
It looks like you’ve amended the CSS already to reflect, but for anyone else reading this you should set your margin values in numerals instead of “none”
margin-left: 0;
Also, there’s no such thing as text-align:float-right; but both of these are correct (yielding very different results):
float: right;
text-align: right;