Core Web Programming, Second Edition

5.12. Layers

Netscape 4 supports a capability known as layers which allows you to place HTML markup in separate rectangular regions, then to position the regions at particular absolute or relative positions on the page. Regions can overlap, and upper regions can be transparent to let lower regions show through. Layers let you create overlapping banners and sidebars, make multicolumn text, annotate diagrams and other pictures, and create composite images by placing transparent GIFs on top of other images. Furthermore, you can use JavaScript to dynamically make regions visible or invisible, to change the stacking order, or to shrink, expand, or move regions on the screen. The specifics of how to change layers dynamically is covered in Chapter 24 ...