undefined tag

💾 replit

css

:not(:defined) { 
    display: block; 
    width: 120px; 
    border-bottom: 2px dotted red; 
    text-align: center;
    background-color: hsla(60, 80%, 50%, 0.4);
} 

:not(:defined):before { 
    content: "undefined <tag>"; 
    color: red; 
}

html

<my-element></my-element>

📗 參考

• pseudo-class