CSS Class (a phrase I hate)

I keep seeing the term “CSS Class” crop up, but it doesn’t have any official meaning. It doesn’t even have a consistent unofficial meaning. I’ve seen the phrase “CSS Class” applied to mean all of the following:

• HTML class
• CSS class selector
• Any CSS selector
• A CSS rule set

Often it is possible to work out what people really mean, but that isn’t always the case. This is an appeal — if you find yourself saying or writing “CSS Class”, please think about what you actually mean.