Diagnostic CSS rules for finding poorly formed, non-semantic, inaccessible markup on links and buttons, mostly. For more diagnostics, check out http://www.tomato-root.com/sandbox/holmes/ and https://github.com/diagnosticss/diagnosticss

gistfile1.scss

@mixin heydon_rules {
    
    // Adapted from http://coding.smashingmagazine.com/2013/08/20/semantic-css-with-intelligent-selectors/
    // I removed the Comic Sans font declaration because, well, I really can't stand it, even in this context
    
    %uglystyle {
        display: block !important;
        background: pink !important;
        padding: 0.5em !important;
        color: #000 !important;
        //font-family: 'comic sans ms', cursive !important;
    	//font-size: 16px !important;
    }
    
    // Rule 1: “If it’s a hyperlink, it should have an href attribute.”
    a:not([href]):after {
        @extend %uglystyle; 
        content: 'Do you mean for this to be a link or a button, because it does not link to anything!';
    }
    
    // Rule 2: “If it’s a hyperlink and has an href attribute, it should have a valid value.”
    a[href=""]:after, a[href$="#"]:after, a[href^="javascript"]:after {
        @extend %uglystyle; 
        content: 'Do you mean for this link to be a button, because it does not go anywhere!';
    }
    
    // Rule 3: “If it uses a button class, it should be a button — at least in the accessibility layer.”
    .button:not(button):not([role="button"]):not([type="button"]):not([type="submit"]):not([type="reset"]):after,
    .btn:not(button):not([role="button"]):not([type="button"]):not([type="submit"]):not([type="reset"]):after, 
    a[class*="button"]:not([role="button"]):after {
       @extend %uglystyle; 
       content: 'If you are going to make it look like a button, make it a button, damn it!';
    }
    
    // Rule 4: “If it is an a element with role="button", then it should link to somewhere when JavaScript is off.”
    a[role="button"]:not([href*="/"]):not([href*="."]):not([href*="?"]):after {
       @extend %uglystyle; 
       content: 'Either use a link fallback, or just use a button element.';
    }
    
    // Rule 5: “You can’t disable a hyperlink.”
    a.button[class*="disabled"]:after, 
    a.btn.disabled:after,
    a[class*="button"][class*="disabled"]:after {
        @extend %uglystyle; 
        content: 'You cannot disable a hyperlink. Use a button element with disabled="disabled".';
    }
    
    // Rule 6: “Buttons in forms should have explicit types.”
    form button:not([type]):after {
    	@extend %uglystyle; 
    	content: 'Is this a submit button, a reset button or what? Use type="submit", type="reset" or type="button"';
    }
    
    // Rule 7: “Both hyperlinks and buttons should have some sort of content or an ARIA label.”
    // Buttons and links that don’t include any kind of direction for their usage are pretty bogus.
    a:empty:not([aria-label]):not([aria-labelledby]):after, 
    button:empty:not([aria-label]):not([aria-labelledby]):after, 
    button:not([aria-label]):not([aria-labelledby]) img:only-child:not([alt]):after, 
    a:not([aria-label]):not([aria-labelledby]) img:only-child:not([alt]):after {
        @extend %uglystyle; 
        content: 'All buttons and links should have text content, an image with alt text or an ARIA label';
    }
}