Fix: Simpler CSS2 starfield background-positions

• Switch to simpler CSS2-style `«length» «length»` background-positions (from CSS3-style `left «length» top «length»`) because the compatibility and consistency is supposed to be better.
	» Originally, I put this in to try to alleviate %-positioning issues.  Now we're just using `px`s, because the percentages were bitches.