An exercise in debugging Cascading Style Sheets

We launched a new version of the work website this week. We’re still tweaking things, but overall, I like the look of it, especially the subpages. The report pages haven’t looked this good in ages. I think I’ve kind of fallen in love with Open Sans, the font used in the new design, and I like that it comes in both bold and semi bold versions.

Just before we launched, though, we ran into one of those wonderful head scratchers that seem to be the hallmark of web development. We were clicking through the various views, and Garry clicked into the screen to edit an address. In IE, (of course) there was nothing there except the Save button at the top of the page. Since the section is loaded via Ajax, my first thought was that it was some sort of problem with loader script, especially since I was seeing Javascript errors in the error console. I found that error, fixed it, but it still didn’t fix the page.

Brute Force Debugging

Obviously, since we were dealing with a new theme and a new style sheet, those could be the culprit. So was it the new HTML or the new CSS? Turning off CSS showed the form, but was that issue?  Nothing obvious leapt out at me, and I had no idea where to even start looking. Finally, I bit the bullet, saved a backup copy of the stylesheet, then deleted the last third of it. No luck. I reinstated the section I deleted, then deleted another section. Still no luck. Finally, removing lines 400 to 700 revealed the form. From there, it was a simple matter of removing smaller and smaller parts of the stylesheet, until we zeroed in on the offending line.

Here it is:

main .controlbar .minibutton, main .controlbar .minibuttonactive {width:auto; display:inline;  text-align:center;  margin: .07em 0 .34e7em}

Do you see it?

The problem arose out of the fact that, for accessibility’s sake, we’re using ems instead of pixels (px) as units of measurement, because they make it much easier for a user to resize their screen. Pixels tend to be simple integers; ems are often decimals, and in a longish decimal, a typo can hide. In this case, the margin should be

margin: .07em 0 .347em

Once I narrowed into the right line, it was immediately obvious. Nearly an hour to find, 10 seconds to fix.