<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style> html, body { width: 100%; height: 100%; background: #000; } </style> </head> <body> <!-- <div class="c1" style="width: 50%;height: 50%;"></div> --> <div class="c1" style="width: 310px;height: 320px;"></div> </body> </html>