The problem has occured because you have used invalid code.
You have wrapped block level elements up inside your h2 tag which is not allowed and is confusing ie.
Change your code tyo something like this.
You should set up a class for that inline style to keep things tidy, I've just left it there so you can see it .
<div style="position:relative;z-index:100"><h2>limited edition giclee <a href="java_script_:;" onClick="MM_showHideLayers('giclee','','show')" onMouseOver="MM_swapImage('question','','http://www.jaypaulstudio.com/images/question-roll.gif',1)" onMouseOut="MM_swapImgRestore()"><img src="http://www.jaypaulstudio.com/images/question.gif" alt="What is GiClee?" name="question" border="0" id="question"></a>
<div id="giclee" class="definition" onMouseOut="MM_swapImgRestore();MM_showHideLayers('giclee','','hide')" >Giclee
prints are ditigal copies of original artworks, made using high-resolution
digital files and inkjet printers. For more information, visit <a href="http://www.proteusworkshop.com/giclee.html" target="_blank">Proteus