When Should I Use Quotation Marks in CSS Attribute Selectors?

Understanding CSS Attribute Selectors: Quotation Mark Dilemma

When crafting CSS selectors that target elements based on their attributes, a common question arises: Should quotation marks be used when specifying attribute values? This article delves into the intricacies of this aspect based on the CSS specification.

According to the CSS specification, using quotation marks around attribute values is not always necessary. In general, unquoted alphanumeric values can be used. However, there are exceptions to this rule:

• Values containing spaces require quotation marks.
• Values starting with certain characters, such as Hyphens (-) or Periods (.) should be quoted.
• Values starting with a number or containing mathematical operations need quotation marks.
• Values generated with the attr() function or containing Unicode characters should be quoted.

To avoid potential inconsistencies, it's a good practice to enclose attribute values within quotation marks. By doing so, the selector is guaranteed to work correctly in all cases. Examples of valid attribute selectors include:

• a[rel="nofollow"]
• a[rel='nofollow']
• a[rel=nofollow]

For additional clarity, you can refer to the CSS specification chapters mentioned in the linked article. Remember, this guide provides comprehensive details on the nuances of unquoted attribute values in HTML and CSS.

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