Change height of the UIWebView component

In my app, I am opening an URL in an UIWebView. I wanna change the height of a particular component. The source of the page has,

<div class="main-container scrollable animated animated-fast transparent fadeIn" ng-class="{fadeIn:done}"><-></div>

I want to change the css height property of <div class="main-container scrollable animated animated-fast transparent fadeIn" ng-class="{fadeIn:done}">. How do I access that in swift?

I tried,

webView.stringByEvaluatingJavaScriptFromString("document.getElementsByClassName('main-container scrollable animated animated-fast transparent fadeIn')[0].css('height', '100%');")

But not successful.