The problem of empty div occupying space under IE6/7_html/css_WEB-ITnose

I haven’t been paying attention to the front-end recently. When I encountered such a problem at work, I subconsciously wrote font-size:0;line-height:0; but I didn’t know it caused a bigger bug. Later, when the data was inserted, it was no longer displayed. . Later, Baidu found out that it turned out that just writing an empty div inside would be enough. The principle is not yet clear, I will do a little research when I have time