CSS: The value is out of range.This value must be between “0” and “100”'.

A percentage value in your CSS exceeds the allowed range of 0 to 100.

CSS properties that accept percentage values — such as opacity, width, height, and others used in certain contexts — may be restricted to specific ranges. When you embed CSS in an HTML document (via the style attribute or a <style> element), the W3C HTML Validator checks these values and flags any that fall outside the permitted range.

A value like 100.01% is just slightly over the maximum of 100%. This is often a typo or a rounding error. While most browsers will silently clamp the value to 100%, it is still invalid and should be corrected.

HTML Examples

❌ Invalid: value out of range

<div style="width: 100.01%;">Content</div>

✅ Fixed: value within range

<div style="width: 100%;">Content</div>

Learn more:

MDN Reference

MDN Web Docs: CSS values and units

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MDN Reference

MDN Web Docs: percentage

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MDN Reference

MDN Web Docs: opacity

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