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Part: IV Dynamic HTML: Layers, Cascading... > Using Dynamic HTML and Layers - Pg. 246

246 Chapter 15. Using Dynamic HTML and Layers What You'll Learn in This Hour: · · · · What layers are, how they work, and how they are used How to add a layer and position it on the page How to set the stacking order, background color, and visibility of a layer How to use Dreamweaver timelines to add animation to a web page Dynamic HTML (DHTML) provides you with the flexibility to lay out your web pages and make them interactive. Dreamweaver's layers provide a way to control where objects are placed on the page. You can place items precisely where you want them, without having to create elaborate tables. Layers are the more modern way to position content on a web page. I use them extensively in the sites I create. You don't have to pick between tables and layers. You can use both in a web page, taking advantage of the strengths of each. Layers are not meant to stretch to fit the screen, whereas tables can be set to a percentage of the screen, allowing for stretching to different screen resolutions. Unlike a table cell, layers are autonomous and can be moved individually. You'll experiment with layers and be able to compare them to what you've learned about tables in Hour 12, "Displaying Data In Tables," and Hour 13, "Designing Page Layout Using Tables." What Is DHTML? DHTML enables you to create an interactive experience for the web page user. DHTML isn't an official term; it's a term used by web developers to reference a collection of technologies used together to produce a more interactive web page. The three main components of DHTML are layers, Cascading Style Sheets (CSS; see Hour 16, "Formatting Web Pages Using Cascading Style Sheets"), and JavaScript (see Hour 17, "Adding Interactivity with Behaviors"). DHTML is an extension of HTML that gives web page developers greater control over page layout and positioning. DHTML also allows greater interactivity without depending on interaction with a server. When people talk about DHTML, they usually mean the combination of HTML 4 (as defined by the W3C Web standards organization) and CSS. These elements work together through a script- ing language, usually JavaScript. Here's a short list of the types of things you can accomplish using DHTML: · Add to your page images that are hidden from view that will appear when the user clicks a button or a hotspot. · Create pop-up menus. · Enable the user to drag and drop an object around the screen at will. · Cause text to change color or size when the user rolls her mouse over it.