防止块元素的背景在浮动内容后面流动

I have a block element floated to the left with various block elements to the right of it. These non-floated elements have backgrounds on them which are showing behind the floated element. I'd like to prevent that from happening. Normally I'd achieve this with a margin-left on the elements but I'd like the elements which are below the floated element to use the full width of the container (otherwise it'll just look like two columns with white-space beneath the floated element).I have a block element floated to the left with