xxxxxxxxxx<html><head><meta name="viewport" content="width=device-width, initial-scale=1.0"><style> body { background-color: lightgreen; } @media only screen and (orientation: landscape) { body { background-color: lightblue; } }</style></head><body> <p>重置浏览器大小，当文档的宽度大于高度时，背景会变为浅蓝色。否则为浅绿色。</p></body></html>