A tool like http://csslint.net can help point out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problematic patterns or signs of inefficiency. The rules are all pluggable, so you can easily write your own or omit ones you don't want.
All applications to be tested against user browsers, and screen resolutions
- Chrome (v. 38 and above) – for public sites and student applications
- Internet Explorer (v. 7 and above) for faculty and staff applications
- Safari (v. 8 and above)
- Firefox (v. 35 and above)
- 1280px x 700px for desktop applications
- 360px x 640px for mobile applications
Test your site for responsiveness
Make your site work with different screen sizes. Use tools like http://responsivepx.com/ which has controls to adjust the width and height of the viewport to find exact breakpoint widths in pixels. Then use that information in your media queries to create a responsive design.