Caching problem of javascript with servlet

Hi guys
There is a problem of caching with the our project. This project contains two servlets first is getAdServlet and second is richMediaServlet. getadservlet is called thru <script src=""> following is the code:
<script LANGUAGE="JAVASCRIPT" src="http://192.168.1.6:8080/advert_java/servlet/GetAdServlet?region=1&zone=1&type=nossi&cachevar=yes">
</script>
getadservlet returns the javascript statments. These javascript statments are able to create an <iframe>. Now cotents of the iframe are supplied by the second servlet ie richMediaServlet. This servlet is called like
iframeURL = fullHttpDir+"/servlet/RichMediaServlet?";
iframeURL += "bannerCode="+ RNBanner;
iframeURL += "&cachebust="+ cachebust + refresh+"&getAd=y";
iframeURL += "&hheight="+hheight+"&wwidth="+wwidth;
out.println("document.write(\"<iframe src='" + iframeURL + "' height=" + hheight +" width="+ wwidth + " SCROLLING=no FRAMEBORDER=0 MARGINWIDTH=2 MARGINHEIGHT=2 onfocus='window.focus(); return iframeFocus()'>\");");
out.println("document.write(\"</iframe>\");");
This richmediaServlet returns HTML into <iframe>. when richmediaservlet is called, a parameter 'bannerCode' is passed. then richmediaServlet fatches the banner from the database and displays the banner into the <iframe>.
Now the problem is when i run the html file containing the script tag mentioned above, and supply different bannerCodes from getAdServlet to richMediaServlet then first banner is cached and displayed every time.
i have also used the following code to prevent the caching of both the setvlets
     long currentTime = System.currentTimeMillis();
     response.setHeader("Cache-Control", "no-cache, must-revalidate");
     response.setHeader("Pragma", "no-cache");
     response.setDateHeader("Last-modified", currentTime);
     response.setHeader("Expires", "Sat, 6 May 1995 12:00:00 GMT");
and following in the iframe's head tag before the iframe tag in the getAdServlet.
out.println("document.write('<head>');");
out.println("document.write('<meta http-equiv=\"Cache-Control\" content=\"no-cache,must-revalidate\">');");
out.println("document.write('<meta http-equiv=\"Pragma\" content=\"no-cache\">');");
out.println("document.write('<meta http-equiv=\"Last-modified\" content=\""+ currentTime + "\">');");
out.println("document.write('<meta http-equiv=\"expires\" content=\"Sat, 6 May 1995 12:00:00 GMT\">');");
out.println("document.write('</head>');");
this problem does not arises when i call the getAdServlet from a testServlet and run the testServlet thru get request.
pl tell me what's wrong i m doing.

First, post your code in tags if you want people to read your code...

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