I had some issues in Firefox recently. I was building a complicated “item” in CSS and it looked great in Chrome. I got an email later saying that the sizing was all off for a bunch of things. I thought this was really strange. I went back to the CSS and Chrome and I could not see any issues.

I then fired up Firefox and, yikes! There was a bunch of weird issues. This is strange because normally Chrome to Firefox translates pretty well. I was using the ::first-letter element and a few ::before elements. But somehow, someway they got messed up. Anyway, I discovered this little snippet:

@-moz-document url-prefix() {
  /* firefox only styles */

It works. But what does it mean? The url-prefix() is a way to serve specific styles to a specific URL. In this case, I just want to target a -moz- device. Here is a more in depth definition. This worked nicely, and so it will stay into production.