I think you misunderstood me.
Let me try again..
Usually, with more width, #header has 90px of height. I want #content to show bellow #header so I’m adding padding-top:90px to #content.
In my example I didn’t float my list items just to show the problem in the mobile version. In mobile, with less width, #header is more than 90px height so #content is overlapped by #header.
What I’m asking is if there is any way to push #content again to the bottom of #header, just using CSS and no JS, so I don’t have any overlapping.