[Vince]

You should know that the <center> tag has been deprecated for a while. Adding <br> for stylistic reasons is also not done. That's what CSS is for. If you're just starting to learn something then you shouldn't start with deprecated tags and lazy hacks.

Код HTML:

<section id="widget">
    <iframe width="800" height="800" scrolling="no" src="http://widget.mibbit.com/?settings=8b71c0d91bc8459f780f947ef2ad92d4&server=irc.tl&channel=%23UoS.Echo%20%23UoS"></iframe>
</section>

CSS:

Код:

#widget {
    width: 800px;
    margin: 50px auto;
}

The above is the common method to center a block element (<section>, <div>, <p> etc.) within its parent container (body in this case).

You can add another section with buttons above the current section.