A rollover, also called a mouseover, is an element on a web page that changes when you place your mouse over it. Rollovers are typically graphic or text elements that indicate a link or some other type of active area on a site.
I like rollovers on a site. I think they can be cool and fun and they let me know when part of the page ‘is alive’. For example, if it’s a link to another page or something like that. Our WorldStart site has rollovers on the links. Check it out: www.worldstart.com  . Take your mouse pointer over the “Home”, “Software Store”, “Computer Tips”, “Newsletters”, “Message Board”, or “Contact” links at the top of the WorldStart home page and you will see that the words change from white to light blue.
Here are a couple of sites that have fun rollovers:
http://www.stink.com/  – this is a crazy little site. The bug on the main page is set to do something different each time you roll over it. This rollover is just for fun – it doesn’t link to other pages.
http://www.etch-a-sketch.com/ – this site is a bit graphic heavy but has fun rollovers. The first page asks you to enter your name and then hit “go”. If you enter in your name and hit “go” then the next page appears and your name will be drawn out on a big etch-a-sketch –fun! Anyhoo – there is a lot of spinning, flashing fun rollovers on that page. Put your mouse cursor over them and check them out. These rollovers are also links to the other sections of the site.
If you understand the whole java-thing and are using a web site design program that allows you to easily incorporate them then you are a smart cookie and already ahead of the game J . However, one thing you need to watch out for is the design of the rollovers.
A graphic rollover involves at least two different images – an original image and one that appears when a mouse rolls over it. You can also have an image for when you roll off and one for when you click it. It’s up to you J . These images need to be that exact same size otherwise they will ‘jump’ when you rollover them. Unless that ‘jump’ is part of your design then it just comes across as being poorly designed.
Here are the two images I’m using for my rollover. They are the exact same size with just a slight difference in one of the images to make it look like it’s moving when put into the rollover. Notice that one image has both ears up and the other has one up and one down.
Here is an example of the rollover created with the above two images. You’ll notice that the only thing that moves is Lily’s ear. That’s the only thing that I want to move in this rollover – her ear.
The example below is what happens when the files are two different sizes. Her ear still moves but the whole picture jumps. It’s not what I intended and looks a little weird also.
So, as long as your image files are the same size and your rollovers will look great