Here's one of the most important thing to learn about layers- how to script them. After all, its the scripts that make layers come alive. To access a layer, you need to use the following syntax:

document.layername

Accessing the layer is just the first step. Once you've accessed a layer, you can then go on and manipulate one of the layer's attributes to produce dynamic effects. I'll show a simple example where a layer's background color interchanges between red and blue:

Here's the source code:

<layer id="test" width=80px height=80px></layer>

<script language="JavaScript1.2">
//variable that helps alternate between red and blue
var thecolor=true
//Apply a bgColor of blue as the initial layer color
document.test1.bgColor="blue"
function changecol(){
//if thecolor=true
if (thecolor)
document.test.bgColor="blue"
else
document.test.bgColor="red"
//set thecolor to the opposite of its current state
thecolor=!thecolor
setTimeout("changecol()",1000)
}
changecol()
</script>

All of the layers' attributes are read/write, so be sure to experiment with each of them!