To use max-width the syntax is:

selector {max-width:value;}

Internet Explorer up to version 6 doesn’t support the max-width property but has the ability to perform javascript like functions on it’s CSS so you can fake max-width with it. Here’s the syntax:

selector {width: expression(this.width > value ? value: true);}

example for IMG html tag:

img {
max-width:390px;
/* IE Image max-width */
width: expression(this.width > 390 ? 390: true);
}

NOTE: max-width property does NOTHING for the file size if used with an image.