Category Archives: oocss

Guest on The Big Web Show

me on the big web show with zeldman and benjamin

This week I had the good fortune to spend an hour talking with Jeffrey Zeldman and Dan Benjamin about all things CSS on The Big Web Show. It was lively and fun despite my cell phone making weird noises during the podcast. (Ooops, sorry!)

We talked about progressive enhancement, carpentry, testing, rounded corners, oocss, performance, working on big sites, and being a girl on the internets. If you missed the live show, you can check out the video podcast. I was super-duper-over-the-top nervous about the show, but I’ve heard that I didn’t come off like a total dweeb. ;)

Top 5 Mistakes of Massive CSS

Last week, Stoyan Stefanov and I spoke at Velocity Conference about optimizing massive CSS. We talked about our experiences optimizing large-scale sites like Facebook and Yahoo!, and we discussed our findings regarding the CSS efficiency of the Alexa Top 1000 websites.

Velocity was kind enough to share videos of the session:

What is the state of the internet regarding CSS performance? Kind of sad. We aren’t getting a lot of the basics right, and when we look at the more advanced techniques, there are some spectacular examples of what-not-to-do. Why do we care about CSS performance? As Stoyan talks about in the beginning of the video, it blocks progressive rendering and it is very difficult to auto-minify.

The Basics

These basic rules, made famous by YSlow, have been around for a long time, and yet our data showed that many sites in the Alexa Top 1000 are still not employing the most basic techniques.

  • 42% Don’t GZIP CSS
  • 44% Have more than 2 CSS external files
  • 56% Serve CSS with cookies (yummy to eat, bad for static content)
  • 62% Don’t minify (check out the YUI Compressor!)
  • 21% Have greater than 100K of CSS

CSS Weight for the Alexa Top 1000 Sites

More Advanced Techniques

I talked about these more advanced tests for the first time at Velocity. Here is how the top 1000 sites stack up and some recommendations for reasonable results.

Occurrences in one page
Declaration Max Percentage too many
> 10
Percentage sites *way* too many
> 100
float 733 56% 13% If you have a good nestable grids system, you shouldn’t need many floats. The worst offender in the Alexa Top 1000 sites declared the float property more than 700 times! Aim for less than 10.
h1-6 511 56% 9% There are only so many usable font sizes on the web. Below 10px in most fonts is legible only by mice and few sites use really large typography as a design element. Imagine that a site chooses to use 24px as their max. That leaves 14 different sizes, however, we need to divide that number by two because most users can’t see subtle differences like a 1px change in font size. That leaves seven different heading sizes, which means 56% of sites in the Alexa top 1000 have too many heading declarations.
margin: 0 518 64% 14% Different browsers have different default stylesheets. These stylesheets define how elements should look if you haven’t chosen an alternate style. It is important to get all browsers to the same starting point because it eliminates bugs and time wasted testing simple browser compatibility issues. This is should be accomplished using a reset stylesheet such as the one included in YUI. When a reset stylesheet isn’t used, margin zero tends to be sprinkled throughout the stylesheet as developers try to cope with browser differences in the absense of an abstracted solution. Setting the default margins to zero is the most basic job of a reset stylesheet, which means that 64% of the Alexa Top 1000 sites could benefit from including reset.css.
padding: 0 510 62% 10% Excessive declarations of padding zero are similar to margins (see the above description). The worse offender in this case declared padding zero 510 times.
font-size 889 78% 23% Headings (h1-6) often get hidden in class names, which can disguise typography efficiency issues. It is helpful to grep "font-size" to get an idea how many hidden headings exist on the site. The same rules apply to font-size that were explained under h1-6, so in fact the problem is much worse than our initial estimate. These figures mean that 78% of the Alexa Top 1000 sites have excessive heading declarations when we consider hidden headings. In addition, 22% of sites may not be getting the SEO benefits of properly using heading elements.
!important 526 12%* Important overrides all other declarations specificity, so it can be dangerous. If used correctly, only on leaf nodes, it can be a powerful tool for creating typography and spacing mixins that stand outside of the normal cascade. On the other hand, excessive use of important is a sure indication of specificity wars. Specificity wars are what happens when developers start trying to beat each others specificity, rather than having a real solid architecture and code standards. Eventually, like the worst offender in this case with 526 important properties, you can end up in a case where nearly every property is marked important. This means that 12% of the Alexa Top 1000 Sites probably has an internal specificity war in it’s web team.

* >50

Happy perf optimizing!

The media object saves hundreds of lines of code

What is the internet made of? At least the UI layer is mainly composed of media blocks. I talked about the Facebook stream story before, and all the tiny objects of which it is composed. For the most part, the stream story is made up of the media object repeated over and over.

The media object is an image to the left, with descriptive content to the right, like this Facebook story:

image to the left, descriptive content to the right

The media object

The content area on the right can contain any other objects. In this case, it contains text, but we could put lists, grids, or even other media objects inside. As we’ve seen before, there are actually many different versions of the media block on the Facebook website (and on most websites). These five are just a few examples of the way this object might be used:

Variations on the media object

Sometimes the image is a tiny icon, a large video, or an avatar, but it is the same basic object. When I’m building a new object, the first thing I do is to figure out which parts are reusable components, and define what I know and do not know about them.

what do we know?

  • Can be nested
  • Optional right button
  • Must clearfix

What have we decided *not* to know? (Think flexibility!)

It is equally important to define what is flexible, or unknown, about a new object.

  • Image width, margins, and decoration vary
  • Right content is unknown
  • Width unknown

Once it is built, we can use it to create many of the same basic object. In the following image, I’ve highlighted all the media objects on the facebook homepage. You can see that even implementing this one object can save a ton of code because we stop repeating ourselves.

media block use

The media object highlighted in red on the facebook homepage

Implementation Details

How does it work? The hard part is making sure that the image can be any width, so that the element is reusable. It means our content area needs to be flexible so that it can fill in all the remaining space available. We’ll have to create a new formatting context to make a flexible column.


<div class="media attribution">
<a href="" class="img"> <img src="" alt="me" /> </a>
<div class="bd"> @Stubbornella 14 minutes ago </div>

The CSS:

/* ====== media ====== */
.media {margin:10px;}
.media, .bd {overflow:hidden; _overflow:visible; zoom:1;}
.media .img {float:left; margin-right: 10px;}
.media .img img{display:block;}
.media .imgExt{float:right; margin-left: 10px;}
  1. We clearfix both the wrapper element, media, and the inner content wrapper, bd (body) using the secret benefits of overflow. There are other ways we could have implemented the clearfix plus new formatting context. More on that in a later post.
  2. Then we float our image wrapper (generally a link) left and our optional right region to the right.
  3. Finally, we set some margins and paddings to keep everything lining up nicely. You might choose to set margins via a class which extends the .img object if you have several different kinds of images with different spacing and decoration.

Voila, we’re done. It is a very simple object, but it is very powerful. We can eliminate a lot of lines of code abstracting this repeating pattern. The code for the media block and many other “web Lego” are available on the Object Oriented CSS open source project.