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The speed of loading pages from the server is an important factor of website usability. In order to provide high speed of page loading, web designers try to minimize the use of “heavy” graphics in website design to the largest possible degree. For that graphic files are replaced using special effects with DHTML. DHTML (Dynamic HTML) is an improved dynamic version of HTML, that allows to create visual effects.
What visual effects for website design are available in DHTML?
DHTML allows web developers to add visual effects to their web pages that are otherwise quite hard to achieve. For instance, DHTML allows the page author to:
- Animate images and in the document, independently moving each element from any starting point to any ending point, following a path chosen by the user or a predetermined one.
- Embed a ticker that automatically refreshes its content with the latest news, stock quotes, or other data.
- Use a form to capture user input, and then process and respond to that data without having to send data back to the server.
- Include drop-down menus or rollover buttons.
Let us give an example. To create buttons with animation effects (for example, change of the button color during mousing over the button) you usually have to create at least three different images:
- the image of the initial button
- the image of the button that is displayed during mousing over the button
- the image of the button when it is pressed
If the size of every image is small enough, about 3 or 4 kilobytes, the total “weight” of all three images will comprise 9 or even 12 kilobytes. If the number of buttons, which have been animated this way, is big enough, the total “weight” of the page will also increase to considerable degree; it makes the loading of the whole page much slower.
If you use opportunities, provided by DHTML, for creation of an animated button, the animation effect will be reached not due to the change of images, but due to the execution of a client-side program function. It means, that the time of page loading will not increase.
Use of DHTML for creation of visual effects on the site does not have a considerable influence on the process of site loading; it brightens up the external appearance of the site and is easy to realize. However, not all the browsers support DHTML; that is why in some browsers visual effects powered by DHTML will not be displayed.
TAGS
website design,
web design,
usability,
dhtml,
visual effects |
website design 
