W3C CSS Selectors API- The querySelector() and querySelectorAll() methods. Last updated: June 4th, 2014. The querySelector() and querySelectorAll() methods let you. 5.8 Attribute selectors. CSS 2.1 allows authors to specify rules that match elements which have certain attributes defined in the source document. CSS Selectors. In CSS, selectors are patterns used to select the element(s) you want to style. Use our CSS Selector Tester to demonstrate the different selectors. CSS Selectors. CSS selectors allow you to select and manipulate HTML elements. CSS selectors are used to find (or select) HTML elements based on their id, class. W3C CSS Validation service enables you to check your CSS code for validity, and warns you if you are using browser specific code. Pattern Meaning Described in section First defined in CSS level * any element Universal selector: 2 E an element of type E.