Iam trying to use the Ext Js in visual force page.I have downloaded the ExtJs SDK 4.1.1a file.and iam uploading the file into static resources.As there is a size limit of 5 mb for each file in static resource i deleted some of  the files in Ext JS SDK 4.1.1a. I have kept some of the files like resources and all the js files into a folder extjs.zip and uploaded into static resource.But it is not working....

My code is as follows

<apex:page >
<link rel="Stylesheet" type="text/css" href="{!$Resource.ExtJS}/resources/css/ext-all.css" />
<script type="text/javascript" src="{!$Resource.ExtJS}/ext-all.js"></script>
<script type="text/javascript">

Ext.onReady(function(){

Ext.Msg.show({
title: 'Milton',
msg: 'Have you seen my stapler?',
buttons: {
yes: true,
no: true,
cancel: true
}
});

});

</script>
</apex:page>

please help me regarding the issue..