js Layer Utility
Javascript Layer Sequence Builder

What are Layers?

In terms of web documents layers are what you use to superimpose web content (html) over existing web pages or emails.   They operate like sheets of glass stacked atop of one another.  Layers combined with a moderate amount of javascript can create animation effects similar to sprites. (this is exactly what the js Layer Utility does).

The content of layers may be changed dynamically via javascript (the js Layer Utility can do this as well)