Saving a file

[motivated]

I'm lost on learning this linux !!   I'm trying to save a file (info.php) in : /var/www/html   Each time I try to save it I get a pop-up saying that the file could not be saved, make sure I have write access and/or theres enough disk space.   I have "NO" idea if I have write access although I cant see why not, all I can say is that I can save it to the desk top, and this linux is real frustrating.   When I first installed mandrake 10.1 I set it up to automatically log me in, is there any way I can set this thing up so that I have access to everything ?   Even logged in as "su" I cant do anything, I only want to see if php/apache is working   Regards Kelvyn