Can I use HTML in my wiki pages?
Yes, you CAN ! Insert your code as "html" or "css" type on any page and you can use in your wiki on any page in an "iframe" tag these /code/-blocks like another url ! See http://piotr.gabryjeluk.pl/dev:a-lot as an example
Without html coding: Only <span> and <div>, and those must appear as [[span]] and [[div]].
Can I insert more than one blank line before/after a paragraph?
Insert following line for every blank line - this will end as lines containing only <br />
How can I embed music and video in my wiki?
See Embedding Media