A layer is a container for HTML content that can be positioned at an exact location in the browser window. Layers can contain text, images, plugins, and even other layers. Anything you can put in an HTML document you can also put in a layer. Layers are especially useful for putting things on top of each other or to make them overlap.
You can show and hide layers with behaviors to create fast pages that change without reloading content from source files. You can make layers move or change in time with the Timeline.
You can open the file created in this ShowMe movie from a browser, or you can open it in Dreamweaver by choosing Help > Open Example and selecting !layers_example.htm.
Layers are a Dynamic HTML feature supported by 4.0 or later browsers. Earlier browsers display layer contents without positioning. See Converting a file to 3.0 browser compatible for information about retaining positioning in older browsers.
Microsoft and Netscape both support the CSS specification for layers defined by the DIV and SPAN tags. Netscape also supports a proprietary layer format rendered by the LAYER and ILAYER tags.
You can create layers within other layers (called "nested" layers) to group them together. A parent layer expands to display the contents of nested layers.
For more information about each type of layer, see Dynamic HTML overview.