Issues while setting up Eclipse with Flex SDK

Issues while setting up Eclipse with Flex SDK

I am following this post
(http://www.seanhsmith.com/2010/03/29/flex-for-free-setting-up-the-flex-4-sdk-with-eclipse-ide/)
for setting up of Eclipse with Flex. Am using Flex 4.6 SDK and Eclipse IDE
4.3. As per the instructions in the post, when I am putting the code
snippet
<?xml version="1.0" encoding="utf-8"?>
<s:Application
xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx">
</s:Application>
in the application.mxml file, the editor is unable to recognise xml, flex
and mx. Eventually, the compilation is failing. Probable issues might be?