What are layers?
A layer is a container that can hold text, tables, images and other multimedia. The advantage of using layers is the flexibility they provide when controling the placement of objects on a page.

The <layer > thml tag has greatly depreciated in the past five years. It is no longer used is most web authoring tools as a way to create "layers" in a web page. Instead when layers are inserted into a webpage using dreamweaver a modified div tag is used to create alyer effect. It shares the same properties as a traditional layer but is essentially controled using inline styles within the DIV element.

Although using inline css avouids issues of standards compliance (browser bugs and accessibiliy problems) it is not the best choice for creating multimedia rich content. As chnages to the styling of "layers" must be applied to each layer in a page and each page that containsd layers. Then all changed files must be uploaded to the web server. This can make routeen maintenece of web pages that contain layers a real head ache.

The recommneded alternative is to use external style sheets to control the style of "layer" treating them more like blocks that appear when specific media is present in a page. See [ media dependent style sheets CS3].

For example:


Limitations and Problems Associated layers

• No relative positioning
• Not all browsers render layers correctly

Layers
Can be used to create rich applications such as dynmic popup menus image viewers however the way layers behave in browsers can sometime be unpredictable for this reason flash is used as the prefered way of creating rich dynamic content for web pages..

The origin for the coordinates used to position layers is in the top left hand corner of the screen.
Note the z index doesn must be in order but does not need to be consecutive.

Due to the fact that layers use absolute references to position themselves in a browser window when ther browser window is resized layers do not adjust thier position this can be problematic whe used with for liquid layout that are commonly used in blogs.
It is recommended to use css styling instead of using layers.

Working with layers

[Create a new layer]
[Set layer position]
[Set layer z coordinate]
[Create a nested layer]
[Set layer color]
[Set lauyer visibiliy behavour]
[Show & hide layers]
[Convert a layer to a table]
[Create a layer animation (swoop in)]