There was a question in the DNN forums today about how to display a wait indicator while an IFrame was loading its contents. My solution:

<script language="Javascript">


function toggleProgress(progressId, iframeId)
{
     objProgress = document.getElementById(progressId);
     objIframe = document.getElementById(iframeId);

     if ((objProgress) && (objIframe))
     {
           objProgress.style.display = (objProgress.style.display == "none" ? "block" : "none");
           objIframe.style.display = (objIframe.style.display == "none" ? "block" : "none");
     }
}

</script>

<div align="center"><img id="<%= ClientID %>_ProgressBar" src="<%= TemplateSourceDirectory %>/images/progress.gif" style="display:block" /></div>

<iframe id="<%= ClientID %>_ResultsFrame" onLoad="toggleProgress('<%= ClientID %>_ProgressBar','<%= ClientID %>_ResultsFrame')" src="http://www.dotnetnuke.com" style="display:none"></iframe>