While completing the tech edit on the 2nd edition of the PHP Anthology the issue of linking came up; specifically, linking to authoritative reference material on the web. [...] The issue isn't simple one. Regarding PHP, the php.net manual is the authoritative reference site. The various web technology standards are also represented by authority web sites.

So what does he thing makes for a good, trustworthy resource? He includes criteria divided up into three sections - readability, accuracy & trustworthiness and longevity.

I know many of you all know pretty well that floating point precision and computers don't play nicely with each other. [...] I was working with a piece of code today at the office that was throwing an error saying two values weren't zeroing out when they clearly should have been.

In his code he shows the simple bit that he was using to evaluate if the result of subtraction would come to a certain value. In the comments, others share similar experiences and one even recommends another option to make things a bit more accurate - the bcmath library.