Percentage values

It's probably just to the fact that, the more precise you get, the less gaps and "white spaces" you would find. As you can never go 102% of total width without having a horizontal scroll bar or just that 99.89% isn't the same as 100% when it comes to precision. On smaller screens that point-something % could be insignificant but at some point it might render something worth 10 or even 20 pixels of unused or unspecified space with some high-density or wide resolution viewports.

As long as that doesn't matter to you, it should be ok to round up or down. :) Again, as I said back in another post, this is just my 2 cents and opinion. I might have been misled at something believing such would be the case (as I've asked myself the same question when I first saw that, but then came to that conclusion.).

Thanks, Evandro. I follow your logic. Those extra pixels definitely matter to me. But I can't help but wonder what originally caused the need for that many decimal points? If you use whole numbers for all of your padding/margins, wouldn't that allow you to stick with whole numbers?

For example, if you set a margin of 5% and a padding of 10%, the width of the viewport would be 70% (since 5x2 + 10x2 = 30% worth of padding/margins)

Is it because he used pixels in some cases? I'm no math whiz, but I could see how that might break the percentage values into numerous decimal points.

Well, there we go. That was, in fact, the reason. But as we learn there, there might be no real point to use precision above 3 decimals or maybe we could consider using the calc() CSS function and provide the 3 decimals fallback option for older browsers.

I think that Guil just tried to illustrate that decimal precision on percentages DO matter. From there we learn it and adapt it to real world needs. :)