I can't get the iFrame embed widget to work

This is probably idiotic human error (mine!), but I can't get the iframe embed widget to embed this onto my form: http://typing-speed-test.aoeu.eu/iframe.plp

I have tried every variety, the url above, this: <iframe

    src="//typing-speed-test.aoeu.eu/?iframe=1;lang=en"

    width="700"

    height="300"

    style="border: 0;"

>

Could you please provide us with the form ID or URL in question so we can inspect it and assist you further? Thank you in advance.