What are common mistakes of amateur front end web developers?

Can anyone please tell me some of the common mistakes of amateur front end web developers.

The most common mistakes of front-end web developers are as follows:

  • Ignoring Responsive Web design results in a poor user interface, making it difficult for the end-user to read the content or click on the horizontal scrollbar along with many other inconsistencies when viewed from a particular type of device such as smartphone, tablet, etc.

  • Incomplete Input Validation-Incomplete input validation can result in a mistyped alphabet in the details field or some other useless mistake. Web developers sometimes make the mistake of avoiding form validation and trusting user input. End users are individual and can also make mistakes.

  • Cross Browser Compatibility Issues -Cross Browser Compatibility Bugs are sure to happen for any web application, regardless of the platform they use for development. Most notably, they keep popping in every iteration.

  • Outdated HTML-Technology is evolving at an impressive pace, and while we don’t want to change our traditional way of doing things, we need to adapt our web development to keep up with the modern world.