The Top 5 Mistakes of Massive CSS

Web Performance Ballroom AB
Average rating: ****.
(4.76, 29 ratings)

Your website has out-of-control CSS bloat. You know your performance is being impacted, but how do you move from organic CSS with no particular architecture to something lighter, more logical, and easier to maintain? In this session, Nicole Sullivan and Stoyan Stefanov will show you how they improved the CSS at Facebook and Yahoo! Search. After this session you will know how to:

1. Use lint tools to automate and evaluate the efficiency of your CSS
2. Avoid the top 5 causes of CSS bloat, and
3. Speed up your site by making the UI code an order of magnitude smaller.

Photo of Nicole Sullivan

Nicole Sullivan


Nicole is an evangelist, front-end performance consultant, CSS Ninja, and author. She started the Object-Oriented CSS open source project, which answers the question: how do you scale CSS for millions of visitors or thousands of pages? She also consulted with the W3C for their beta redesign, and is the co-creator of, an image optimization service in the cloud. She is passionate about CSS, web standards, and scalable front-end architecture for large commercial websites.

She co-authored Even Faster Websites and blogs at

Photo of Stoyan Stefanov

Stoyan Stefanov


I work for Yahoo!’s Exceptional Performance team. My daily tasks include research, experiments and building tools (such as YSlow) to improve the performance of the Yahoo! properties worldwide. I’m also a contributor to several open source projects and author of a few books and numerous online articles. Creator of the ( online image optimization tool.

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Picture of Nicole Sullivan
Nicole Sullivan
07/03/2010 10:28am PDT

@Sam – Yes! Once you realize that, most UIs start to look like the same repeating patterns, and repeating patterns can be optimized. It really changes everything.

Sam Ghods
06/24/2010 8:00am PDT

Most impressive talk on CSS I’ve seen. Revelation of PHP objects != CSS objects is huge. Definitely can make a huge improvement on how we do things.

Picture of Jon West
Jon West
06/24/2010 6:45am PDT

Excellent talk with refreshing ideas on how to engineer CSS for more efficient, less painful development. I either missed or didn’t remember Nicole’s talk last year but I’m glad i made it this year!

Picture of Mark J. Levitt
Mark J. Levitt
06/24/2010 6:41am PDT

I learned a lot in this talk, thanks so much! I also appreciated Stoyan’s intro which really spelled out the justification for Nicole’s points.

Picture of Steve Souders
Steve Souders
05/19/2010 6:19am PDT

This is the must-see talk for me. I’m not bad at JavaScript, but my CSS is all over the place. Nicole has been evangelizing CSS best practices for years. These best practices not only improve performance, but also lead to better maintainability and reuse. I worked with both Nicole and Stoyan on the Exceptional Performance team – they know what they’re talking about. You can also see Stoyan at his session Psychology of Performance .

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