Webcenter Portal Display issues in lower versions of IE

I have a portal application developed in JDev 1.6. While running the application, it supposed to be 

displayed full of the browser and it is in Firefox, Chrome and even in IE (version greater than 8). But 

I have a requirement to use this in IE7. When I run this app in IE7, the app is displaying in one third 

of the browser. To make my app displays properly in IE7, I need to write some browser specific 

javascript. Below is my javascript code added to my home page. This script will be executed when 

the browser is IE and its version is 7.

<af:resource type="javascript"> 

browser_version= parseInt(navigator.appVersion);

browser_type = navigator.appName;

if (browser_type == "Microsoft Internet Explorer" ) {

if((browser_version == 4)){

var lineURL = "&lt;style&gt;.af_decorativeBox { width: 100% !important;height: 640px

 !important;}div.af_decorativeBox_center{overflow: hidden !important;}div.af_panelTabbed_body {overflow: auto;}.profileSubHeader{ margin-left: -10px !important}.wid50 input {width: 35px !important;}&lt;/style&gt;";

document.write(lineURL);

}

</af:resource>

In the above code, lineURL is a variable which holds css styles which will impact my display in IE7.