Just look at the width and height settings you have. On the first one, it's much smaller than what you posted:
<iframe class="preview-frame" src="http://salafiwales.co.uk/wp-content/themes/Chameleon/liveEvents/event.php?id=1" height="<font color='"#FF0000"'>240</font>" width="<font color='"#FF0000"'>320</font>"></iframe>
You can change those values. It's best to keep them in proportion, but you can also adjust them until there's no scrolling.