CSS Border Help

CSS is very serious. lol.
I am working on the
I’m having an issue with the img class and using
.thick-green-border {

Hello, you have not explained your problem, in any case your arguments are empty. You must put values ​​for example:

border-color: Yellow;

You haven’t stated anything yet, no values. Kindly check it up.

Check out the w3school.com website. It’s got everything there is in html & css.
Click https://www.w3schools.com/css/css_border.asp for information about borders.