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.

IE7 and IE8 hack behavior

We’ve had the luxury of hacks to fine tune Internet Explorer bugs. Internet Explorer 7 disabled the majority of hacks, with the exception of the * hack. This hack allowed you to send a style only to Internet Explorer by prefacing an attribute with an asterisk.


/*this is for all browsers*/
#main p {color:black;}
/* this is for Internet Explorer */
#main *p {color:red;}
/*this is ignored by IE7 and will target IE6 */
#main _p {color:green;}

This set of hacks allowed us to control IE7 and IE6. However, IE8 does not recognize the * hack. Special IE8 rules will either need to be defined with conditional comments, the Microsoft proposed meta tag, or some new hack to be discovered. Let’s hope the mature version of IE8 will reduce the need for these hacks.

For more information on the above hacks, visit an earlier post: IE7 Hacks

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! Hack Day – Paxilled

There’s a special buzz around the halls of Yahoo! today as Hack Day is about to begin. We have 24 hours to build, modify, or tweak the existing Yahoo! Technologies. We can also go outside the box and build new technologies.

Hundertwasser pathway in Vienna

I have decided to go way, way, way outside the box with my hack. I’m hacking the lexicon, the dictionary, the world of slang. I’m bypassing the world of code and trying to use the social network world to add a new word to our vocabulary.

Paxilled

Pronunciation: ‘paks-seld’
Function: adjective
  1. Resembling the common side-effects of Paxil® medication: blurry, anxious, confused.
    Sample Uses
    The new Tarantino film left me paxilled
    The site launched with a crowded, paxilled navigation menu
    The lensbaby gives photos a paxilled effect
  2. Medicated with Paxil.
    Sample Uses
    Susan is happier with her paxilled hubby.
Uses

This hack is about the web’s social network capability. Consider this an invitation to use the word and publish it.

Here’s what you can do:

  • Visit www.paxilled.com for the full definition and links to progress results.
  • If you use Flickr , add the tag “paxilled” to images that are… paxilled. These could be images that are blurry, confused, hectic, anxious… The image could be perfectly normal but represent a paxilled person, place or thing.
  • Join the new Flickr photo group: paxilled
  • Use paxilled in a blog post and add the tag “paxilled”. Use paxilled in other types of publications.
  • Use paxilled in your daily conversation.
  • Add paxilled to wikipedia, urban slang dictionary, or any other online resource center that you think may be appropriate.

If you have something online, share it with a comment on this post.

IE7 background sprite bug – the saga continues

I’ve been able to narrow down my problem with IE7b2 and background sprites. However, I still have not been able to create a stripped down test page that consistently mis-behaves. So my observations, while not scientific, could save you some hours of debugging.

Internet Explorer 7beta2 is not treating transparent png background images correctly. It sees “background-position: 0 0” as “background-position: 0 100%”. Come to think of it, I have only tried a vertical sprite, this may be the same for a horizontal sprite.

What’s the solution?

You could create a series of rules in your IE7 style sheet to measure your new sprites from the bottom up, instead of top down. But this doesn’t solve some of the other odd issues with IE7 and transparent png images. I’ve seen the images load upside down and I’ve seen the images move when you scroll the page and the image hits the bottom of the browser. I thought I was going crazy or that I had some sort of mutated version. But this pseudo-animation works on other computers.

Our IE6 style sheet replaces our pretty alpha transparent png graphics with a simpler index transparent gif version. We replaced our re-measured rules in the IE7 with this set and it has solved our problems. It would be great to take advantage of IE7’s ability to use alpha transparent png images, but this bug is just driving me nuts. I’ve also been in contact with the IE7 team. They are dedicated to building the best browser possible within their constraints and hopefully this will be figured out before the final launch of IE7.

One other note of advice. Creating alpha transparent png images via the save as command in Photoshop on a Mac gave us the worst results. Those images did some very funky things on the page. Fireworks created better images.

c’est fini!

I don’t know if it is official or not, but I can say that the Microsoft engineers are interested in what developers have to say and have worked on this bug. I believe it has been fixed and will be all good to go with the final release of IE7. I can’t confirm or deny this, but I am pleased with their response to my initial post and followup.This bug has officially been officially fixed as of Release Candidate 1 and you can use your transparent png sprites without a worry in the world!