Day76Focusblur.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Day76</title>
    <style>
        .invalid { border-color: red; }
        #error { color: red }
      </style>
</head>
<body>
    Your mailid: <input type='email' id='mail'>
    <span id='error'></span>
    <Script>
       mail.onblur=function(){
           if(!mail.value.includes('@')){
               mail.classList.add('invalid');
               error.innerHTML='please enter the valid mail address'
           }
       }

       mail.onfocus=function(){
           if(this.classList.contains('invalid')){
           mail.classList.remove('invalid');
           error.innerHTML='';
           }
       }
    </Script>
</body>
</html>