CSS: “font-style”: X is not a “font-style” value.

The font-style CSS property controls whether text is displayed in a normal, italic, or oblique face from its font-family. It has a limited set of accepted values, and the W3C validator will flag any value that falls outside this set.

This error commonly occurs for a few reasons:

• Confusing font-style with font-size: Since both properties start with font-, it’s easy to accidentally type font-style: 1.2em when you meant font-size: 1.2em. Numeric and length values are not valid for font-style.
• Confusing font-style with font-weight: Writing font-style: bold is invalid because bold is a font-weight value, not a font-style value.
• Typos in keyword values: Misspelling a valid keyword, such as font-style: itallic or font-style: oblque, will trigger this error.
• Using the oblique angle syntax incorrectly: While oblique can accept an optional angle (e.g., oblique 10deg), providing an angle without the oblique keyword or using an invalid unit will cause a validation error.

Using invalid CSS values can lead to unpredictable rendering across browsers. Most browsers will ignore the entire declaration when they encounter an invalid value, meaning your intended styling won’t be applied at all. Keeping your CSS valid ensures consistent behavior and makes debugging easier.

Valid font-style values

The accepted values for font-style are:

• normal — displays the normal face of the font family.
• italic — selects the italic face; falls back to oblique if unavailable.
• oblique — selects the oblique face; optionally accepts an angle value (e.g., oblique 10deg). The angle defaults to 14deg if omitted.
• Global CSS values: inherit, initial, revert, revert-layer, unset.

Examples

Incorrect: size value applied to font-style

This is the most common mistake — using a length value that belongs on font-size:

<p style="font-style: 1.2em;">This text has an invalid font-style.</p>

Correct: use font-size for size values

<p style="font-size: 1.2em;">This text has a valid font size.</p>

Incorrect: using bold with font-style

<p style="font-style: bold;">This text has an invalid font-style.</p>

Correct: use font-weight for boldness

<p style="font-weight: bold;">This text is bold.</p>

Incorrect: misspelled keyword

<p style="font-style: itallic;">This text has a typo in font-style.</p>

Correct: properly spelled keyword

<p style="font-style: italic;">This text is italic.</p>

Correct: using oblique with an angle

<p style="font-style: oblique 12deg;">This text is oblique at 12 degrees.</p>

Quick reference for commonly confused properties

If you’re unsure which property to use, here’s a quick guide:

You want to change…	Use this property	Example value
Italic or oblique text	font-style	italic, oblique
Text size	font-size	1.2em, 16px
Text boldness	font-weight	bold, 700
Text decoration	text-decoration	underline, line-through

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