images and display: none

Opera and Safari download the image when you switch the display to block.

When image has display: none or is inside an element with such a declaration, the browser may opt not to download the image until the display is set to another value.

This page contains two hidden images. If you saw two alerts when you entered the page your browser downloaded them immediately.

Open test1, a pure img tag.

Open test2, a div containing an img tag.