It’s incredibly common. There’s even tools available online that compare segments of code so you can copy/paste two different code blocks and it will highlight the differences for you. The longer and more complex code sections become, the more likely you will miss a bracket, semi-colon, or have a simple typo.
Many editing environments also come with automatic highlighting features, so if you have an element or word selected it will highlight all instances of that word, and you can quickly see a typo when something is not highlighted that should be.