Design vs Style
Style can be very subjective. What appeals to one person may not appeal to another. Style can be appealing or non-appealing.
Design can be good or bad. Their are guidelines and rules that you can learn and follow. Expert designers have learned which guidelines and rules that they can bend or break under which circumstances.
You can learn to be a good designer. Pay attention to details. Follow the rules. You may not be ground breaking but your users will feel comfortable with your websites and apps.
Bad designers do things randomly. They fall back on their own style. They use the colours and fonts that appeal to them. They say things like "I love this shade of green and this shade of orange so I am going to use both of them as my website colour scheme.
Examples of Good Design
99Designs is a website where designers can showcase their work as well as compete for jobs. Clients will ask for a logo or website design and put money in escrow for the work. Then the competition begins. The winner of the contest gets the money promised.
There are some excellent designers with work on this site. Many very talented designers get their start here.
Here are a couple examples of designers with great work.
Want to practice your CSS skills?
Try to replicate some of their designs using HTML and CSS.