Out of pure curiosity:
Assuming tabulated data in HTML is being generated by a PHP script, would it be better to alternate each row's background color with PHP or rely on JS to do it?
One is run client-side and the other server-side so my guess you have to take the whole web app as a whole and see which side should be spared the additional workload. Is it situational or is there an absolute rule?
In a vacuum, I guess you could argue PHP would be better since it cannot be turned off in the way JS can (unless plugins like NoScript can block PHP as well), but I don't have enough experience with either to be sure.