Solution to the invalid margin-top element in the div tag_HTML/Xhtml_Web page production

As title.

The question is very strange. The upper-level tag of the element is div, and attributes such as width and height have been set. However, when the margin is used to adjust the element, it does not take effect. Classmates’ experience suggests that the problem is solved by setting the parent element attribute of the element to

overflow:hidden;

.