You cannot change the browser styles for disabled buttons in IE, but you could wrap your button like this:
<div class="button-wrap">
<a class="button" disabled="disabled"><span>My button</span></a>
<span class="visible-text">My button</span>
</div>
Then position and style visible-text as you want preventing that weird movement you say. Something like this:
.visible-text {
position: absolute;
cursor: pointer;
color: green; /* or whatever... */
}
Using visibility: hidden on the default button text keeps the width of the button so you can position there the same text without any problem.
a.button span {
visibility: hidden;
}
Please try it here:
http://jsfiddle.net/fnwjT/47/