css - div设置float：left后高度设置自动会无效 ？

Question

.main_box_rightbox {
    width: 950px;
    height: auto;
    float: left;
    margin-left: 5px;
    margin-top: 3px;
    position: relative;
}

这样之后mainboxrightbox 高度只有16px
这是为什么？？
有内容！！

Answer 1

Floats not cleared?

.clear{clear:both;}

Answer 2

I can’t see all your code. I estimate the possible reasons:
1. The float is not cleared, causing the height to not be expanded.
2. The content is empty, causing the height to not be expanded. height:auto Automatically adjust the height based on the content within the block.

Answer 3

Actually. You can set it in the parent p.
:
p {

overfloat: hidden;

}

That’s it. No need to use clear floats.

Answer 4

Because you set position:relative, if the child element is positioned in absolute position, it will not be able to open the parent p