<html><head><style>#example1 { border: 2px solid black; padding: 25px; background: url(mountain.jpg); background-repeat: no-repeat; background-size: cover;}</style></head><body><h2>background-size: cover:</h2><div id="example1"> <h2>Hello World</h2> <p>调整背景图像的大小以覆盖整个容器，即使它必须拉伸图像或从其中一个边缘切掉一点。</p></div></body></html>