HTML Guides for font-style

The font-style and font-weight properties serve different purposes. font-style controls whether text appears in a normal, italic, or oblique style, while font-weight controls how thick or thin the characters are rendered. Writing font-style: bold is a mistake because bold is not among the accepted values for font-style. Browsers will ignore the invalid declaration entirely, meaning your text won’t become bold at all — it will simply render in the default weight.

This error typically comes from confusing the two properties or misremembering which property handles boldness. The valid values for each property are:

• font-style: normal, italic, oblique, or oblique with an angle (e.g., oblique 10deg)
• font-weight: normal, bold, bolder, lighter, or numeric values from 100 to 900

To fix this issue, replace font-style: bold with font-weight: bold. If you intended to make text both bold and italic, you’ll need to use both properties separately.

Examples

Incorrect — using bold with font-style

This triggers the validation error because bold is not a valid font-style value:

<p style="font-style: bold;">This text won't actually be bold.</p>

Correct — using font-weight for boldness

Move the bold value to the font-weight property:

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

Correct — combining bold and italic

If you want text that is both bold and italic, use both properties:

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

Correct — using font-weight in a stylesheet

You can also apply bold styling through a <style> block or external stylesheet, using either keyword or numeric values:

<style>
  .emphasis {
    font-weight: bold;
  }
  .light {
    font-weight: 300;
  }
  .heavy {
    font-weight: 900;
  }
</style>

<p class="emphasis">This text is bold (weight 700).</p>
<p class="light">This text is light (weight 300).</p>
<p class="heavy">This text is extra heavy (weight 900).</p>

Note that the keyword bold is equivalent to the numeric value 700, and normal is equivalent to 400. Numeric values give you finer control over text weight, especially when using variable fonts or font families that offer multiple weight variations.

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: