Often you might want to replace the standard sumbit button on a html form with an image.
This is a very simple thing to do.
Instead of:
<input name="submit" type="submit" value="submit" />
insert:
<input alt="Search Button" src="image.jpg" type="image" />
Here is an example of such a form:
<form method="POST">
<input name="searchtext" type="text" />
<input alt="Search Button" src="search.jpg" type="image" />
</form>