The first step in creating a scalable application as well as a user-friendly application is to reuse classes, they're your best friend! Create a class dictating a re-useable border bottom on an element that's used often. .re-border-bottom { border-bottom: solid black 3px; }

The best website to find good colors is materialize, as it supplies modern, well-complementing and contrasting colors. Don't over-use the colors as they'll create your website moving from a nice mix of greyscale to a supercharged spectrum of colors!

See how the header image has the same border bottom as the other images? Repetition. Always use the same classes and never use the inline styling unless it's a page-unique element. This causes confusion for people editing your code, they not only have to account for a stylesheet, but inline styles!