Create focus.md

As focused is not great context with a test for current focus

Author: HelenBurge

pages/glossary/focus.md

@@ -0,0 +1,12 @@
+---
+title: Focus
+key: focus
+unambiguous: true
+objective: true
+input_aspects:
+  - CSS styling
+---
+
+An element is said to have _focus_ when the element matches the [`:focus` pseudo-class](https://drafts.csswg.org/selectors-4/#focus-pseudo) uninterruptedly for a period of 1 second after a user stopped interacting with the page.
+
+The 1 second time span is an arbitrary limit which is not included in WCAG. Given the possibility of the focus state of elements being managed through scripts, testing the focused state of an element consistently would be impractical without a time limit.