Progressive enhancement of links using the CSS attribute selector

Attribute Selector Test Page

We have avoided using CSS3 rules for too long. It’s been difficult to justify using rules that won’t work for a significant portion of our audience, Internet Explorer 7 and below. However, Internet Explorer 8 is coming out soon and does work with the features we like.

I think it’s fairly safe to assume IE7 users will upgrade to IE8 within a short time. Those stuck with IE6 for one reason or another will slowly disappear as they are given new computers or their locked down environments are upgraded.

So, with the future of CSS3 functionality within reach, I’ve been energized to begin experimenting again. I’ll be writing a series of blog posts over the next few months that look at CSS3 functionality as a progressive enhancement. How can we continue to deliver a perfectly fine web site to IE6 and IE7 and mobile phones while enhancing the functionality of more modern browsers and devices?

Attribute Selectors

CSS attribute selectors are the golden ring on the web development merry-go-round. They can be daunting to learn, addictive to use, but then disappointing when you realize they are out of your grasp when you test in Internet Explorer. We can, however, begin using them to add additional functionality based on your pre-existing, semantic code. Attribute selectors give you power to write CSS that pinpoints the stuff you already code, without having to go back and add classes or ids. I’ve written previously about using attribute selectors to let your users know the language of a site they are about to visit. This trick relies on the rarely used hreflang attribute, which identifies the language of the site targeted in a link.

There are many other attributes in your HTML, from table headers, image src, link titles, and selected options. Think about all of those juicy attributes just waiting to be targeted. Also think about how you could actually do something useful with them.

Announce the file type of a link with CSS

I once worked for a company that had hundreds of thousands of static HTML pages in their intranet. With no content management system; it was impossible to make global changes. The only thing they shared was a common set of style sheets. Does this sound familiar? Follow along as we increase your site’s usability in a less than perfect, but efficient way.

First off, for accessibility, you need to let users know when a link will open a file, what type it is, and how large it is. This is best done by adding it to your HTML code:


Foo presentation (.pdf, 5kb)

That delivers the information to everyone, regardless of their browser. This, however takes time and is a daunting task for updating legacy code.

We can, however, use the atttribute selector to target the extension of the link to display the icon and insert the text describing the file type. Here’s the sample HTML code:


It’s a simple list of links for different types of files. We’ll be looking at the extensions: .zip, .pdf, .doc, .exe, .png, and .mp3. Feel free to extend this list to any extension you so desire. This would be especially helpful for a company that uses proprietary file types within their intranet.

Now, let’s look at the CSS:


a[href$="zip"],
a[href$="pdf"],
a[href$="doc"],
a[href$="exe"],
a[href$="png"],
a[href$="mp3"] {padding-left:20px; background:url(bg-file-icons.png) no-repeat 0 0;}
a[href$="png"]{background-position: 0 -48px;}
a[href$="pdf"] {background-position: 0 -99px;}
a[href$="mp3"]{background-position: 0 -145px;}
a[href$="doc"]{background-position: 0 -199px;}
a[href$="exe"]{background-position: 0 -250px;}

a[href$=".zip"]:after{content: "(.zip file)"; color:#999; margin-left:5px;}
a[href$=".pdf"]:after{content: "(.pdf file)"; color:#999; margin-left:5px;}
a[href$=".doc"]:after{content: "(.doc file)"; color:#999; margin-left:5px;}
a[href$=".exe"]:after{content: "(.exe file)"; color:#999; margin-left:5px;}
a[href$=".mp3"]:after{content: "(.mp3 file)"; color:#999; margin-left:5px;}
a[href$=".png"]:after{content: "(.png file)"; color:#999; margin-left:5px;}
a[href$=".exe"]:after{content: "(.exe file)"; color:#999; margin-left:5px;}

See the final test page.

Pattern matching in the attribute selector

We have some limited “regular expression” functionality in CSS3. We can search for an attribute’s presence and match a pattern within the attribute’s value.
Patrick Hunlon has a good summary of the pattern matching:

  • [foo] — Has an attribute named “foo”
  • [foo=”bar”] — Has an attribute named “foo” with a value of “bar” (“bar”)
  • [foo~=”bar”] — Value has the word “bar” in it somewhere (“blue bar stools”)
  • [foo^=”bar”] — Value begins with “bar” (“barstool”)
  • [foo$=”bar”] — Value ends with “bar” (“I was at the bar”)
  • [foo*=”bar”] — Value has bar somewhere (“I was looking for barstools”)

Attach icons to anything with CSS

The CSS is simply looking to see if the desired extension is at the end of the link href. If so, apply the following styles.

Adding an icon to the link

First, we are match any of the desired file extensions. We then add a background image and some padding on the left side with a bulk rule. Then the background position on the sprite is adjust for each particular link type. Combining multiple icons into one background image reduces the number of files the user has to download, making your page faster. This will work with any browser that recognizes attribute selectors, including Internet Explorer 7. However, support for more obscure attributes may be spotty.

There’s another peculiarity with pattern matching. Some attributes are case sensitive while others are not. The href attribute is NOT case sensitive, so the above rules will also work if your image name was FOO.ZIP, foo.Zip, or foo.zip.

Adding the descriptive text

Now, we are going to add a bit of descriptive text to each link. We can’t describe the file size, but we can tell the user what type of file it is. This is using the :after(content:) functionality and is supported by Internet Explorer 8 (yeah!!!) but not Internet Explorer 7 and below (boo!!!).
We will also adjust the color and give it a bit of spacing.

A big step forward with a small chunk of work

There you have it. A small chunk of CSS coding has now added substantial usability to your legacy pages. While the CSS version is not as accessible as having the data in the actual link code, it’s a significant improvement over nothing at all. Further, there’s no harmful effect on browsers that do not understand the function. You’ve added information, but haven’t taken anything away. This is a win in my book. To save some time and effort, you could just download and use this package of CSS and icons from Alexander Kaiser.

This rather simple example of attribute selectors and pattern matching can open your eyes to many possibilities. There are a number of developers that have been expoloring this potential for the past few years. Take a look at some of these resources for more ideas and have some fun.

UTF-8 compatible accented characters

Sometimes the simplest information is difficult to find. Today I was searching for the HTML entities for French characters. Fortunately, I found the following resource French Encoding and Language Tags from Penn State.

Here’s an example of the information available on the Teaching with Technology site:

  Lowercase Vowels
à à (225)
â â (226)
ä ä (228)
è è (232)
é é (233)
ê ê (234)
ë ë (235)
î î (238)
ï ï (239)
ô ô (244)
œ œ (156)
ù ù (250)
û û (251)
ü ü (252)
ÿ ÿ (255)

Teaching and Learning with Technology

Internet Explorer 8 beta released for testing

The MIX 2008 conference is this week and Microsoft is showing off some of their latest tools. One of these is the much anticipated and discussed Internet Explorer 8 browser. It’s important to remember that this is still a beta 1 release and is much better than the IE7 beta 1. This one actually has significant changes.

Download Internet Explorer 8

You can download Internet Explorer 8, Beta 1 from the Microsoft Developer site. However, here are a few things to keep in mind:

  1. This installation takes some time, about 15 minutes, and will require a restart of your computer.
  2. It will replace your existing Internet Explorer and is not available as a stand-alone browser.
  3. It renders in standards-mode as a default. You’ll see a button to render in IE7 mode. This is helpful to see the changes between the versions.
  4. Many sites will have significant layout issues in the standard view. You may need to re-evaluate your conditional comments to specify IE7 instead of greater than IE6
  5. IE8 is ignoring the * hack! This means you can use the underscore hack for IE6, the * hack for IE6 and IE7 and … um… I don’t know yet for IE8.

Is IE8 better than IE7?

It’s still really early to find all of the bugs and benefits of the new browser. The team needs to be commended for the fast development and their willingness to listen to criticism and change the default behavior at such a late point. I look forward to the more mature releases.

Updates

Yahoo! Music – Easy, semantic, unobtrusive music badges

Let’s say you want to link to a song on the internet. Let’s also say that you want your users to easily listen to that music. Further, let’s say you want people to find and enjoy the music without having JavaScript enabled.

Is this asking too much?

Yahoo’s Christian Heilmann has been advocating layered, semantic badging.

Yahoo Music badges and the simple href

Yahoo! Media Player has taken this approach to embedding music. You simply put a link to a music file in your site, insert the music JavaScript and away you go. The Music Badge Twiki also shows how you can extend the functionality with basic HTML elements, such as adding a title attribute or image inside the link.

Here’s an example of the badge in effect. Orca at the Casbah, 1992Orca live at the Casbah, 1992 I made a bootleg recording of Orca, a San Diego supergroup circa 1993. I’m simply going to create a basic link to the music file and include an optional image from flickr. The JavaScript will use that information for the player to appear. You’ll see page loads with a little play icon next to the link. There’s also a small player on the side of the browser. Click on either and you’ll see a media player appear in your browser with the music controls.

Here’s the code:

Orca at the Casbah, 1992Orca live at the Casbah, 1992

RNIB releases guidelines for accessible Flash banner ads

The Royal National Institute of Blind People has just released a set of guidelines for building accessible Flash ads. While these are aimed at ads, there’s no reason you can’t use the same guidelines in all of your Flash projects.

  1. Provide a text equivalent for the animation.
  2. Provide an alternative for the Flash animation
  3. Readability
  4. Looping and blinking
  5. Test your move
  6. WCAG compliance
  7. Navigating Flash with a screen reader

See the full article for more information on these Flash accessibility guidelines.