Hi
First get height of the browser window using jquery and pass that height using css to iframe.
Try like this
<script language="javascript" type="text/javascript">
FixWindowsHeightAndWidth{
winHight = $(window).height();
$('.center').css({ "height": winHight + "px" });
}
window.onresize = FixWindowsHeightAndWidth;
<iframe src="../asptonet/asptonet1.asp?DestPage=../DynamicPages/immunization_annotation.aspx" class="center" frameborder="0" width="100%" id="frm_immunization" name="frm_immunization" SCROLLING="no"></iframe>
Try to get window height for browser or screen using jquery and pass that hegith to iframe use Class or cssclass.So if u resize browser the iframe height also resize based on heigth.
Regards
Aravind