Target all images that have an empty alt tag
img[alt=""] {
/* Rules for <img> elements without alt text. */
}A links without a href attribute
a:not([href]) {
/* Rules for <a> elements without a href attribute. */
}Bonus - Target pseudo selector
For highlighting hash (#) links when they're active in the current URL fragment.
h1:target {
/* Rules for h1 elements matching the current URL fragment. */
}