Articles By: Louis Lazaris

Creating pure CSS tooltips with no images or JavaScript is nothing new. I’ve never personally written anything on the topic, but there are plenty of examples and tutorials to choose from.

For a recent project, I had to research the concept of CSS tooltips and find something that suited my needs. I didn’t spend too many hours researching but, from what I could see, most (if not all) solutions available were satisfactory for most cases, but had a few minor flaws.

So in this post I’ll address these minor weaknesses and present what I think might be a more bulletproof solution.

Three of the attribute selectors in the CSS3 spec allow you to check the value the specified attribute for a string match. These attribute selectors are referred to as substring matching attribute selectors.

These can open endless possibilities, so I think it’s useful to have them in mind. And as a bonus, these selectors have strong support as far back as IE7, so pending thorough tests I think they are quite safe to use in many current projects.

Here’s a brief outline of each one, with some examples.

Due to developers’ habitual reliance on pixel values, I think some of us may not have a full understanding of what the em unit is, and how it works in CSS.

As is the case with many topics I write about, I’ll probably learn a thing or two while writing this. So I hope this will serve as a nice summary of what em units are all about and how you can use them in your designs.