I need some help

Hi i use atom as a code editor for html and i have accidentally set the default program of css to notepad, and now whenever i load up my web-page, css wont work because its default opening program is notepad how can i reset it so it return to its default opening program. Thanks any answer would be appreciated.

Uhm. I doubt your browser asks your os to open the css file.
Sounds like you’re trying to edit it by clicking it from some graphical file explorer since other programs will read the file directly, ignoring what your os thinks is a good program for opening it.
What’s stopping you from changing the file association back? If you can’t find where to change it, then I’m sure googling file association and the name of your os will tell you where you can do that.