NerdTech

Hi, I am very new to php so sorry if this is a simple question. I'm not sure if I can explain it but I'll try my best. I basically have 2 php files with nothing in them but HTML code, one is called table.php and the other is called nav.php. When working on those php files I would obviously like to style them but how can include an external stylesheet?... if I link a stylesheet file in those php files called "main.css" it works. But then when I try and php include the table.php and nav.php in my main.php file it doesn't work, I think because it's linking path is wrong and not only that it then calls the same main.css file twice. I can always link to the main.css in my main.php file but then I lose the styling in table.php and nav.php!! so i guess my question is what is the best way to link a css file from a php document? and then when i php include them in my main.php file it only calls it once etc... -thanks for any help!!!