Part of the reason why How I Met Your Mother is so great is because the writers/producers are aware of details.
Some of Mother's best moments have come from little extra efforts done off screen.
What am I talking about?
-When we found out in one of the seminal HIMYM episodes, "Slap Bet", that Robin was a Canadian pop star in her youth...Robin Sparkles got a MySpace Page. Furthermore, complete length music videos were created out of both Robin Sparkles singles, Let's Go To The Mall and Sandcastles in the Sand.
-When Barney brought up the following website: tedmosbyisajerk.com - this existed too. So does marshallandlilyselltheirstuff.com (redirects to a charity). So does guyforceshiswifetodressinagarbagebagforthenextthreeyears.com. There used to be a Slap Bet Countdown website, which disappeared at some point after the episode aired.
I'm sure I'm missing some other ones, but as you can see, the writers of the program love to create little nuggets for observant viewers to find and enjoy (and they spend time on these things...there's a 20 minute song on tedmosbyisajerk.com). And it's little things like these that make this show a cut above average...