MouseOver effects

I’m a bit new to DHTML and Javascript. I was wondering if someone could give me a simple example of a mouse rollover effect.
Let’s say I have text or an image (whatever is easier) of the word “Hello”. When I roll over it I would like either text or an image(again whatever is easier) to show up somewhere else on the page saying “Hello There”. When my mouse leaves the word Hello, “Hello There” disappears.

Thanks

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