Some older browsers knew a little about JavaScript but couldn’t handle image effects. This line checks to see if the JavaScript code can detect any images on the page.

The image probably isn't loaded by that time. I mean, it's probably a couple milliseconds, if that, between when you assign that src and when you ask for the width and height.

The first image (before rollover) has been given the name button1.This code says that the chgImg function is called by both the onMouseover and onMouseout event handlers, both of which pass ...

Researchers have discovered a relatively new way to distribute malware that relies on reading malicious obfuscated JavaScript code stored in a PNG file’s metadata to trigger iFrame injections.