form2.html

<html>
    <head>
        <script type="text/javascript">
        function fun(){

var a=document.getElementById("txt");

var b=document.getElementById("pass");
if(a.value==""){
    //alert("enter user");
    a.style.border="solid 3px red";
    document.getElementById("lab").style.visibility="visible";
    return false;
}
else if(b.value.trim()==""){
    
    alert("enter pass");
    return false;
}
else if(b.value.trim().length<5){
    alert("pass is too small");
    return false;
}
else{
    return true;
}
        }
        
        </script>
    </head>
    <body>
        <form onsubmit="return fun()" action="ref.html">
        <input id="txt" placeholder="enter_name" type="text"/>
        <br><br>
        <input id="pass" placeholder="enter_pass" type="password"/>
        <br><br>
        <button type="submit">click me</button>
        <label id="lab" style="color: red; visibility:hidden;">Invalid</label>

        
        </form>
    </body>
</html>