Drop cap letters — Makes words harder to read at expense of appearing fancy.
Long vertical menus on blogs — Blogs are intended to be read. Long, sticky, vertical menus on your blog distract users from your content. If you must add a vertical menu, make sure that your content is more visible than your menu items.
Multi-layer menus — Minimize clicks and work people have to do to navigate. Make your menus items as easy to understand as possible, and minimize layers for better usability.
Semi-highlighted words — Makes words harder to read at the expense of appearing fancy. Use a bottom border that is below the words instead.
Burger menus — People who are using your website for the first time have enough surprises. Instead of a mysterious burger menu, list your menu items with descriptive names and make them visible on all pages and accessible with one click.
Tiny text — Design your content so your grandma can read it.
Light-colored text on white screens — Not enough contrast. Use colors that are more opposite each other, so people don't have to squint to read your content. Don't use a light gray text for your content.
Progress bars for a resume — By stating how much progress you have made in something, you're making the assumption that you know how much skill you have relative to knowing everything possible about a subject. For almost any skill, there will be things you know, things you know you don't know, and things you don't know you don't know. Compared to claiming to know your incompetencies, assuming ignorance is the smarter move.
Giant irrelevant pictures and autoplay videos — Slows your site down and wastes data for no reason. Resize your pictures so they are the same size as they appear to the user. This will make your site load much faster and make your users happy.
Heavy sites with no consideration for user data usage — Build things for people in 3rd world countries. Data is expensive for some people. Test your web performance with tools like Google Page Speed Insights.
Heavy third party plugins — Test everything that you add to your site from a third party. Many third-party plugins are bloated. It takes less than a minute to test your site's speed and data usage, but can save your users hundreds of hours of time collectively, if you improve your website speed.
Pop-ups that force you to close them — They may increase your conversions, but ruin your user experience.
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