Why are dashes preferred for CSS selectors / HTML attributes?

Question

In the past I\'ve always used underscores for defining class and id attributes in HTML. Over the last few years I changed over to dashes, mostly to align m

Answer 1

Perhaps a key reason why the HTML/CSS community aligned itself with dashes instead of underscores is due to historical deficiencies in specs and browser implementations.

From a Mozilla doc published March 2001 @ https://developer.mozilla.org/en-US/docs/Underscores_in_class_and_ID_Names

The CSS1 specification, published in its final form in 1996, did not allow for the use of underscores in class and ID names unless they were "escaped." An escaped underscore would look something like this:

    p.urgent\_note {color: maroon;}

This was not well supported by browsers at the time, however, and the practice has never caught on. CSS2, published in 1998, also forbade the use of underscores in class and ID names. However, errata to the specification published in early 2001 made underscores legal for the first time. This unfortunately complicated an already complex landscape.

I generally like underscores but the backslash just makes it ugly beyond hope, not to mention the scarce support at the time. I can understand why developers avoided it like the plague. Of course, we don't need the backslash nowadays, but the dash-etiquette has already been firmly established.