It might be a caching problem.
If your site is not live yet, and you just want to update the stylesheet
at your pleased intervals, then use this: Ctrl + F5.
On Mac OS (in Chrome) use: Cmd + Shift + R.
This will force your browser to reload and refresh all the resources related to the website's page.
So every time you change something in your stylesheet and you wanna view the new results, use this.