--- id: 6140883f74224508174794c0 title: Step 10 challengeType: 0 dashedName: step-10 --- # --description-- Make the `header` take up the full width of its parent container, set it's `height` to `50px`, and set the `background-color` to `#1b1b32`. Then, set the `display` to use _Flexbox_. # --hints-- You should use the `header` element selector. ```js assert.exists(new __helpers.CSSHelp(document).getStyle('header')); ``` You should give the `header` a `width` of `100%`. ```js assert.equal(new __helpers.CSSHelp(document).getStyle('header')?.width, '100%'); ``` You should give the `header` a `height` of `50px`. ```js assert.equal(new __helpers.CSSHelp(document).getStyle('header')?.height, '50px'); ``` You should give the `header` a `background-color` of `#1b1b32`. ```js assert.equal(new __helpers.CSSHelp(document).getStyle('header')?.backgroundColor, 'rgb(27, 27, 50)'); ``` You should give the `header` a `display` of `flex`. ```js assert.equal(new __helpers.CSSHelp(document).getStyle('header')?.display, 'flex'); ``` # --seed-- ## --seed-contents-- ```html