Leadbolt ad (ad becomes too small)

I've set up an ad account at Leadbolt, used placed the given code in an html, uploaded the html to a server. I'm using this code to display the ad on my iPhone:

// create instance of StageWebView

var _stageWebView:StageWebView = new StageWebView ();

_stageWebView.stage = stage

// set the size and location of the html 'window'

// in this case x = 0, y=0, width = 480px, height = 80px

_stageWebView.viewPort = new Rectangle(0,0,320,50);

// url of html we want to load

var myAdvertURL:String = "http://www.fastgearproductions.com/AdsTest.html";

// load the html page in to our StageWebView instance

_stageWebView.loadURL(myAdvertURL);

It creates a 320x50 big window for the ad, the ad displays but it's soooo tiny. I've tried all the different sizes Leadbolt offers, and I've tried some html examples for changing size in the content displayed... nothing changes anything, the ad remains super small. I've tried it in landscape and portrait mode...

Any ideas?