cleaning up my connection act

Hi, as my first ever attempt at programming I now have a website "working" using PHP and MySQL to produce a lot of dynamic content. My next step is to try and go back, and make the code a little cleaner. I have never understood ( still don't) the connection(s) to the database 1) should each one be closed ' mysql_close() ' as soon as it has served its need, or do they automatically close at the end of a script? ( I worry about overtaxing the server and I really have ZERO idea of how it all works) 2) If I want to make several queries to produce a page, say one as the page starts loading to get data that is used in the WHERE clause of another at the bottom of a page, to different tables in the same database. Do I need to open separate connections for each one? (the PHP is in separate blocks with straight HTML in-between, if that matters) anyway I haven't been able to find any documentation I could UNDERSTAND <G> on connections and how best to use them to not tax the system more than necessary and would appreciate info on that