1. Using Insecure Protocols: Despite advances in web development, some websites still use insecure protocols such as FTP and HTTP, which allow for potential data theft.

2. Poorly Written JavaScript: Many websites are still using poorly written JavaScript code, which can lead to slow loading times, security vulnerabilities and compatibility issues.

3. Ignoring Mobile-First Design: With mobile devices accounting for over 50% of web traffic, it’s essential that websites are designed with mobile devices in mind. Yet, many sites are still developed without considering mobile first principles.

4. Not Keeping Up With Web Standards: The web is constantly evolving, and web developers need to keep up with the latest standards to ensure their sites are up-to-date and accessible.

5. Not Optimizing for SEO: Search engine optimization is essential for any website, yet many web developers still fail to optimize their sites for SEO.

6. Poorly Written Code – Poorly written code can lead to slow loading times, errors, and other issues.

7. Poorly Developed Mobile Sites – Many companies are still not taking advantage of the mobile market, and their sites are difficult to navigate on mobile devices.

8. Ignoring SEO Best Practices – Too many web developers are ignoring SEO best practices, leading to poor visibility for websites on search engine result pages

9. Not Implementing Security Measures – As more web applications become available, developers should be aware of the importance of security and implement measures to protect users’ data.

10. Outdated Design – Web design trends change quickly and websites should be updated regularly to stay current.