<html> <head> <script> window.onload = setBanner; function setBanner() { var w = screen.availWidth; var i = document.getElementById('banner'); if (w >= 1000) { i.src = 'image_big.jpg' } else if (w >= 700) { i.src = 'image_medium.jpg' } else { i.src = 'image_small.jpg' } } </script> </head> <body> <img id='banner' src=''> </body> </html>