It only crashes -or, rather, returns a 'not found' message; CSS has never caused a crash for me in 4.7, though background scripting frequently does nowadays- on valid CSS if the link is improperly written. There are two ways of putting in the link. One leads older browsers to believe that they ought to be loading an html page (this of course fails) while the other works perfectly well. Both are 'standards compliant'. I use the one that works in older as well as newer browsers, and see no reason why other people can't make the elementary effort of doing likewise.

Web developers ought never to forget that W3C has changed 'standards' numerous times in recent years, and older browsers are not 'faulty' because they don't recognise standards that were implemented after they were written. Reasonable backwards compatibility is a virtue, and really not very difficult to implement for those who have the will. It merely requires developers to have a little background knowledge, and the willingness to test their sites properly.