'z-index' is applied to
+----------------+--------------------------------------------------------------+ | Applied_To |<a> <address> | | |<applet> <b> | | |<big> <blockquote> | | |<button> <caption> | | |<center> <cite> | | |<code> <col> | | |<colgroup> currentStyle | | |<custom> <dd> | | |defaults <dfn> | | |<dir> <div> | | |<dl> <dt> | | |<em> <fieldset> | | |<form> <i> | | |<iframe> <inputtype="button"> | | |<input type="checkbox"> <input type="file"> | | |<input type="image"> <input type="password"> | | |<input type="radio"> <input type="reset"> | | |<inputtype="submit"> <input type="text"> | | |<isindex> <kbd> | | |<label> <legend> | | |<li> <listing> | | |<marquee> <menu> | | |<ol> <p> | | |<pre> runtimeStyle | | |<s> <samp> | | |<small> <span> | | |<strike> <strong> | | |style <sub> | | |<sup> <table> | | |<tbody> <td> | | |<textarea> <tfoot> | | |<th> <thead> | | |<tr> <tt> | | |<u> <ul> | | |<var> <xmp> | +----------------+--------------------------------------------------------------+