Website effects

By combining content from HTML, styles from CSS and action with javascript we can produce some useful effects for a website.  This combination is called DHTML (dynamic HTML).  Moving images, popup boxes, timers and hover links are just some of the effects we can make use of.
As I get time I'll extend this list and link in examples

Some useful effects for a website using CSS and Javascript

frame control maintain the correct frameset for your site
form validation Make sure important fields are completed correctly
imagemaps one way of providing site navigation
mouseovers change an image or color of text when the mouse is over it
nav bar help the visitor to find their way around the site
browser check select a stylesheet or page to suit a particular browser
res check select a stylesheet to suit a particular screen resolution
popup windows alerts and other messages plus separate browser screens for images etc.
print this page an easy print button
dynamic content changing text on screen