Developers and designers should avoid providing flashing or blinking text and objects that flash or whose blink frequency is greater than three (3) times per second (WCAG 2) or more than two (2) times per second (Section 508). This also applies to content in video files and content animated using CSS. Such elements can cause seizures and distract users, especially with learning disabilities. In addition, the blink tag element is obsolete and the use of blinking text considered a bad design practice. Blinking text is frowned upon by several usability and accessibility standards and the CSS specification allows browsers to ignore the blink value
Accessibility (WCAG 2 Level AA, 2.2.2)
The checkpoint examines the entire HTML source code of a page and reports any <blink> elements and style definitions that include blinking.