if $debug == true

	// Are there any empty elements in your page?
	:empty
		outline				5px solid yellow


	// Images require `alt` attributes, empty `alt`s are fine but should be
	// double-checked, no `alt` is bad and is flagged red.
	img
		outline				5px solid red
	
	img[alt]
		outline				none
	
	img[alt=""]
		outline				5px solid yellow


	// Links sometimes, though not always, benefit from `title` attributes. Links
	// without are never invalid but it’s a good idea to check.
	a
		outline				5px solid yellow
	
	a[title]
		outline				none


	// Double-check any links whose `href` is something questionable.
	a[href="#"],
	a[href*="javascript"]
		outline				5px solid yellow


	// The `target` attribute ain’t too nice...
	a[target]
		outline				5px solid yellow


	// Ensure any lists only contain `li`s as children.
	ul,
	ol
		& > *:not(li)
			outline			5px solid red


	// It’s always nice to give `th`s `scope` attributes.
	th
		outline				5px solid yellow
	
	th[scope]
		outline				none


	// `tr`s as children of `table`s ain’t great, did you need a `thead`/`tbody`?
	table
		& > tr
			outline			5px solid yellow

	// `tfoot` needs to come *before* `tbody`.
	tbody
		& + tfoot
			outline			5px solid yellow


	// Forms require `action` attributes
	form
		outline				5px solid red
	
	form[action]
		outline				none


	// Various form-field types have required attributes. `input`s need `type`
	// attributes, `textarea`s need `rows` and `cols` attributes and submit buttons
	// need a `value` attribute.
	textarea,
	input
		outline				5px solid red
	
	input[type]
		outline				none
	
	textarea[rows][cols]
		outline				none
	
	input[type=submit]
		outline				5px solid red
	
	input[type=submit][value]
		outline				none


	// Avoid inline styles where possible.
	[style]
		outline				5px solid yellow


	// You should avoid using IDs for CSS, is this doing any styling?
	[id]
		outline				5px solid yellow


	// Definition lists should only contain DT and DD elements
	dl
		& > *
			outline			5px solid red

	dl
		& > dt
			outline 		none

	dl
		& > dd
			outline			none