.php文件不会从.css文件中读取样式

I am making a .php website (text editor, on Ubuntu) and I'm trying to include style.css with html code

<link rel="stylesheet" charset="utf-8" href="style.css" />
<style type="text/css"></style>

which is between tags. For some reason it won't work (neither in Mozilla nor in Chrome). It does work for other php websites that I created before and copied into /var/www/html but not for this one. I've checked other threads and articles on the web, it's not about directories... No idea.

Perhaps I could ask for an advice?

It turned out the problem was about style.css file permissions - only the owner of the file could read&write and the rest could do nothing. I changed all the permissions to read&write and checked 'allow to execute the file as program' and it worked fine.