is it wrong to use atompub to retrieve data

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I'm building a rss feed reader for windows 8 using WinJS.is it wrong for me to use atomPub to retrieve data from a request, I tried getting htmlrequest to work on my windows 8 app, but the Windows 8 HTML5 WinRT App: How to create a small RSS reader in 30min post by David Rousset on taking rss feed data from blog sites. tutorial, ended up not working for me. the part in the code where it uses xhr. I plug in my site. but the app halts at \[code\]var items = rss.responseXML.querySelectorAll("item");\[/code\]The error I get is. "0x800a138f - JavaScript runtime error: Unable to get property 'querySelectorAll' of undefined or null reference"the link i am trying to pull down is http://store.steampowered.com/feeds/newreleases.xmlbut if i use atompub with a \[code\]client.retrieveFeedAsync(resourceUri).done(function (feed)\[/code\]it pulls down, but then i have issues styling some of the items.