Can CSS ID Selectors Use Periods in HTML Elements?

CSS ID Selectors with Periods in Elements

The HTML specification permits the inclusion of periods (.) within an element's ID. However, a direct CSS ID selector rule will fail to apply, raising concerns about potential misalignments between HTML and CSS specifications.

The CSS specification for ID Selectors omits mention of this scenario, leading to speculation that it leverages a compound combination of a tag name and a class selector. For instance, the CSS rule "a.className" targets all anchor tags () possessing the class name "className."

This compatibility issue raises the question of whether it's feasible to use an external CSS file rule to reference an HTML element with a period in its ID. The presumption is "no," as the CSS specification stipulates that a CSS "identifier" lacks the period as an admissible character.

After further exploration of the specifications, it was discovered that the CSS spec allows for backslash () escaping as seen in many other programming languages. This means that the following rule would successfully match an element with a period in its ID:

<code class="css">#some\.id {
  color: #f00;
}</code>

By escaping the period with the backslash, the CSS selector can accurately target the intended element within the HTML document.

The above is the detailed content of Can CSS ID Selectors Use Periods in HTML Elements?. For more information, please follow other related articles on the PHP Chinese website!