Hide horizontal scrollbar on an iframe?

I’d suggest doing this with a combination of

1. CSS overflow-y: hidden;
2. scrolling="no" (for HTML4)
3. and seamless="seamless" (for HTML5)*

^{* The seamless attribute has been removed from the standard, and no browsers support it.}

.foo {
  width: 200px;
  height: 200px;
  overflow-y: hidden;
}

<iframe src="https://bing.com" 
        class="foo" 
        scrolling="no" >
</iframe>