I try this in IE8 with the latest versions
<script src="../js/vendor/jquery-1.10.1.min.js"></script>
<script src="../js/vendor/gsap/plugins/CSSPlugin.js"></script>
<script src="../js/vendor/gsap/easing/EasePack.js"></script>
<script src="../js/vendor/gsap/jquery.gsap.js"></script>
<script src="../js/vendor/gsap/TweenMax.js"></script>
<script src="../js/main.js"></script>
TweenMax.to($('.menu-slider'), 0.5, {css:{left:"0px;"}, ease:"ElasticOut.easeOut"});
Webpage error details
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E; InfoPath.3)
Timestamp: Tue, 29 Oct 2013 02:52:34 UTC
Message: Script error
Line: 0
Char: 0
Code: 0