Performance is a key skill for front-end developers today. New CSS3 and HTML5 features help improve our apps but sometimes these features aren't well supported. This is where Graceful Degradation comes in. You want to leverage the extended features of new browsers but can't afford to ignore support for legacy browsers. I recently started a new project where IE8 support was required. Due to cascade problems when using nested 'EM' units, I decided to start my project using the useful 'REM' units, which are easier to understand and maintain. The main problem with this approach is that IE8- doesn't include support for 'REM' units. Ultimately, I needed to create a fallback for this scenario: in this case, a 'PX' unit fallback.
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