问题
I fixed the header section of a website, but the first div of the page appears behind the header; instead of starting from the end of the header.
回答1:
When you apply position: fixed or position: absolute the element is being removed from the document flow, so the elements that come after treat it as a non-existent. That's why your div jumps up. To fix that apply a margin-top that equals to your header height - http://jsfiddle.net/2xjES/
来源：https://stackoverflow.com/questions/11126482/content-appearing-behind-fixed-header