<!DOCTYPE HTML> <html> <head> <style> body { margin: 0; } #main { width: 500px; height: 500px; opacity: 0.999; background: lime; border: 1px solid black; } .censor { position: absolute; width: 1px; height: 1px; background: cyan; } </style> </head> <body> <div id="main"></div> <div class="censor" style="left:0; top:0;"></div> <div class="censor" style="left:501px; top:0;"></div> <div class="censor" style="left:0; top:101px;"></div> <div class="censor" style="left:501px; top:101px;"></div> </body> </html>