When we’re very focused on working on a web project, we tend to forget or do some mistakes that can lead to an invalid CSS code. I like to call these “Autopilot mistakes”. The kind of mistakes that make us ask ourselves: “Oops, why did I do that?”, and solving them doesn’t take much time, only if you found them in the first place.

I asked on Twitter about the funniest mistakes that a front-end developer can do, and I got some funny responses.

In this article, I will go through some of the most common and funny CSS mistakes that we do while in autopilot.

Mistakes that I do

Font Size

Mistaking between font-size and font-weight is common. Here is the mistake that I do too much.

.title {
    font-size: bold;
}

Opacity

I don’t exactly know the reason, but sometimes I tend to forget the percentage for the opacity value.

.title {
    opacity: 50;
}

Another common issue is mistyping the opacity property.

.title {
    /* It's not easy to spot this */
    opaciy: 0.5;
}

Font Weight

Is it light or lighter?

.title {
    font-weight: light;
}

Padding

This can happen when you think that the property is padding, while in reality, it’s padding-top.

.section {
    padding-top: 10px 20px;
}

CSS Grid

Sometimes, I type grid-column instead of grid-template-columns.

.section {
    grid-columns: 1fr 1fr 1fr;
}

CSS Variables

I don’t why, but I found that I’m too lazy to write var(--brand-color) instead.

.title {
    color: --brand-color;
}

Box Shadow

I always forget that box-shadow should be reset by using none.

.title {
    /* Invalid */
    box-shadow: 0;
}

Also mentioned by Ahmed Hosna

From the community

Visibility

Credit goes to Ori Livni

.title {
    visibility: none;
}

Width

I can’t count the times I did this, and it reminds me of Sublime Text.

Credit goes to bullzito

.title {
    widows: 100px;
}

Offset Properties

There is a weird feeling of abandoning units from CSS offset properties for a positioned element.s

Credit goes to ciruelo

.elem {
    left: 14;
}

CSS Calc()

If the code editor you’re using doesn’t provide proper highlighting, you will miss this one.

Credit goes to Sven Wolfermann

.elem {
    font-size: clac(14px + 1vw);
}

CSS Color

I remember facing such a mistake. Maybe that’s the result of using red to quickly prove something?

Credit goes to TJ Trewin

.elem {
    color: #red;
}

Display

.title {
    display: absolute;
}

Credit goes to Nitin Suresh

Transforms

.title {
    translate: (-50%, -50%)
}

Credit goes to Håvard Bob

I’m writing an ebook

In that regard, I’m excited to let you know that I’m writing an ebook about Debugging CSS.

If you’re interested, head over to debuggingcss.com and subscribe for updates about the book.