<!DOCTYPE HTML> <style> div { background: yellow } div { font-size: 12px; line-height: 1.0; width: 1200px } </style> <!-- Without the patch for bug 707855, we have a 450px container, and the minimum font size at 15em per line is 30px. This means we map 0px-45px into 30px-45px, so 12px gets mapped to 34px. With the patch, then we have a 240px container, so the minimum font size at 15 em per line is 16px. So, we map 0px-24px into 16px-24px, so 12px gets mapped to 20px. --> <iframe src="container-with-clamping-innerFrame-ref.html" width="240" height="400"> </iframe>