<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> html,body{width: 100%;height: 100%;} .c1{ /* width: 100%; height: 100%; */ width: 446px; height: 430px; position: relative; } .c2{ width: 100%; height: 430px; position: relative; } </style> </head> <body> <div class="c1"></div> <div class="c2"></div> </body> </html>