「Bug」Black borders around div el

• Bug
  Div-elements with background color and fixed positioning would get black borders at various zoom values in iOS 7.

• Fixed
  We got rid of the black borders by applying border-radius: 1px; to the container elements which removed all black borders. The value is low enough to not be visible.

事实上，不止ios 7的浏览器上，win7下 FF32.0.1有时也出现过这个问题。
简单来说就是，当div为fixed position且有背景色或者背景图的时候，会出现奇怪黑色线条。这时候用border-radius: 1px;可以暂时解决这个问题。