When I write my sans-serif font-family stack in my CSS file I normally use this:
font-family: Ubuntu, Helvetica, Arial, sans-serif;
Ubuntu is one of my favorite fonts which I import from the Google Fonts CDN, but you can replace it with whatever custom font you want. Since I prefer Helvetica over Arial, it's the next font on the list which I'm hoping they have pre-installed. If not the stack falls back to Arial, then the default sans-serif system font.<...
The CSS transition property allows for a lot of really cool effects in your design but it has definitely caused me to bang my head against the desk a few times. Here are some details about the transition property that aren't very well documented.
Disclaimer: Alright, don't get too excited. This stuff isn't backwards-compatible at all. However, there are fallback solutions and it's pretty darn cool that it's actually being spec'd.
Web designers were begging for CSS to add variables and calculations for years before SASS and LESS came along, giving us the ability to use these shiny new toys to our heart's content. However, SASS and LESS output can sometimes bloat your CSS sheets and while it's pretty fun to play with, it's a pain to have to recompile your CSS after every change. Fortunately, the W3C has come in like the proverbial nanny and started giving them a spit shine to make them all fresh and new again.