This course will become read-only in the near future. Tell us at community.p2pu.org if that is a problem.
For this challange we will be using the site http://jsfiddle.net/
You can write you first HTML-Code there and see results immediately, without installing any programs or other preperation.
There is one more small thing you need to do: find the option "Normalized CSS" in the left hand sidebar and uncheck it. Save again.
This is what your fiddle should look like now:
Congratulations: you now have a place on the web to try out HTML. Just remember he address!