I have a JS function that I want to change the background of a <div> with the id="HLimg". It uses an external stylesheet if that makes a difference.

document.HLimg.style.backgroundImage="url(../images/thumbs/waltdisney.jpg)";

When I run the code I get the error

'document.HLimg.style' is null or not an object

Any ideas?

try this:

document.getElementById('HLimg').style.backgroundImage="url(images/thumbs/waltdisney.jpg)";

Note that I didn't put a '../' before your images folder because it probably isn't needed. That reference only used when targeting a down-level directory, like from an external CSS file that is in its own folder...

Brilliant! Worked like a charm. Thanks!