ID selector
An ID selector is a CSS selector that matches an element by the value of its id attribute.
CSS in Depth, Second Edition
A CSS selector that matches an element by its ID attribute.
- How it is used
- Resolves conflicting CSS declarations by giving an ID-based selector greater specificity than class and tag selectors.
- How deep it goes
- Defines ID precedence, compares selector counts, and stops short of broader cascade details beyond specificity.
- Examples
- Uses #page-title, navigation links, .featured, and competing selectors to demonstrate specificity and targeted overrides.
- What you can do after
- Diagnose CSS conflicts by comparing IDs, classes, and tags, then choose a targeted selector instead of defaulting to !important.
Read how CSS in Depth, Second Edition explains ID selector →
Tiny CSS Projects
An ID selector is a CSS selector that matches the element having a specified ID value.
- How it is used
- Targets one uniquely identified HTML element when a rule must apply to that element rather than reusable groups.
- How deep it goes
- Defines ID syntax, uniqueness, reuse limits, and specificity, but does not develop deeper selector implementation internals.
- Examples
- Uses a blockquote with id="quote-by-author" and styles it with background, padding, and line-height declarations.
- What you can do after
- Apply it via CSS to style a uniquely identified HTML element and judge when a reusable class is more maintainable.
Web Design Playground, Second Edition
An ID selector is a CSS selector that matches the element identified by a specified HTML id attribute value.
- How it is used
- Applies CSS rules to one HTML element identified by its id attribute.
- How deep it goes
- Explains hash-prefixed syntax, case sensitivity, valid id characters, examples, and class-selection guidance without detailing specificity internals.
- Examples
- Uses section-quote and section-summary div elements to demonstrate two distinct ID-based style rules.
- What you can do after
- Apply ID selectors in internal or external stylesheets and choose classes when styles need reuse or easier maintenance.
Read how Web Design Playground, Second Edition explains ID selector →
Related concepts
- CSS selectorkind of · A CSS selector is a pattern that identifies document elements by their names, attributes, relationships, states, or other conditions.
- class selectorcontrasts with · A class selector is a CSS selector that matches elements whose class attribute contains a specified class name.
- CSSuses · CSS, or Cascading Style Sheets, is a stylesheet language for specifying the presentation and layout of structured documents and user interfaces.
- Shadow DOMaddressed by · Shadow DOM is a web platform mechanism for attaching a DOM subtree to an element while encapsulating its structure and styles from the surrounding document.
- cascade layercontrasts with · A CSS cascade layer is a named or anonymous group of declarations whose precedence is explicitly ordered within the cascade.
These guides are generated from the text of Manning books by Manning's knowledge graph and link to the sections they draw on. The full books are available on liveBook and at manning.com.