Untitled

<iframe transparency=true   ...

Column 31: there is no attribute "allowtransparency"

.iframe-trans-fix{
   opacity: 0;
   filter:alpha(opacity=0);
}

<html>
    <body>
        <iframe src="source.html"
                allowTransparency="true"
                style="background-color:lightgreen;"
                width="400" height="200">
        </iframe>
    </body>
</html>

<html>
    <body>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin gravida, magna
           id bibendum sollicitudin, tellus tortor consequat enim, et mollis mauris
           augue et dui. </p>
    </body>
</html>

iframe {
    background-color: transparent;
}

<!--[if lt IE 9]><script> $(".classname").attr("allowTransparency", "true"); </script><![endif]-->

iframe.transparent {
    background-color: #FFF; /*this gives a background color for browsers that can't do RGBA color, like internet explorer*/
    background-color: rgba(255,255,255,0.5);
}

opacity: 0.25; /* all modern browsers */
filter: alpha(opacity=25) /* IE */