try this.. :)
if you have to refresh iframe then give same src once again to iframe
like this....,
html
<iframe height="300px" width="500px" src="www.niravprabtani.blogspot.in">
</iframe>
<span onclick="RefreshIframe()">Refresh</span>
Java script
function RefreshIframe()
{
document.getElementById("MyFrame").src = "www.niravprabtani.blogspot.in";
}