Applying CSS to an iframe

There are two different things here: the style of the iframe block and the style of the page embedded in the iframe. You can set the style of the iframe block the usual way:

<iframe name='iframe1' id="iframe1" src="empty.htm" frameborder="0" border="0" cellspacing="0" style="border-style: none;width: 100%; height: 120px;"></iframe>

The style of the page embedded in the iframe must be either set by including it in the child page:

<link type="text/css" rel="Stylesheet" href="Style/simple.css" />

Or it can be loaded from the parent page with Javascript:

var cssLink = document.createElement("link") 
cssLink.href = "style.css"; 
cssLink .rel = "stylesheet"; 
cssLink .type = "text/css"; 
frames['frame1'].document.body.appendChild(cssLink);