I applied client side validations by using javascript Like

<script type="text/javascript">
        var rname=/^([A-Za-z]\s?)+(\w\s?)*$/;
        var rphone=/\d{10}/;
        var remail=/^([a-z]+\w*)+\@+([a-z]+\w*)+\.+([a-z]*)$/;
        var rcity=/^[A-Za-z]*$/;
        var rstate=/^[A-Za-z]*$/;
        var rcountry=/^[A-Za-z]*$/;
        ErrorText='';
        function myfunction(){
            var sfname=document.getElementById('{!$Component.myform.entry.Patient_entry_section:pafname}').value;
            var slname=document.getElementById('{!$Component.myform.entry.Patient_entry_section:palname}').value;
            var sphone=document.getElementById('{!$Component.myform.entry.Patient_entry_section:paphone}').value;
            var semail=document.getElementById('{!$Component.myform.entry.Patient_entry_section:paemail}').value;
            var saddress1=document.getElementById('{!$Component.myform.entry.Demographic_entry_section:address1}').value;
            var saddresstype=document.getElementById('{!$Component.myform.entry.Demographic_entry_section:addresstype}').value;
            var scity=document.getElementById('{!$Component.myform.entry.Demographic_entry_section:city}').value;
            var sstate=document.getElementById('{!$Component.myform.entry.Demographic_entry_section:state}').value;
            var scountry=document.getElementById('{!$Component.myform.entry.Demographic_entry_section:country}').value;
            if(sfname!=''){
                if(!rname.test(sfname))
                ErrorText+="\n        First name must be start with Alphabates and allows only single space";
            }else{
                ErrorText+="\n        First Name is Required Field it must be Non-Empty";
            }
            if(slname!=''){
                if(!rname.test(slname))
                ErrorText+="\n        Last name must be start with Alphabates and allows only single space";
            }else{
                ErrorText+="\n        Last Name is Required Field it must be Non-Empty";
            }  
            if(sphone!=''&&(!rphone.test(sphone)))
                ErrorText+="\n        Phone number must contain 10 numbers";
            if(semail!=''&&(!remail.test(semail)))
                ErrorText+="\n        Invalid Email formate";
            if(saddress1=='')
                ErrorText+="\n        Address1 is Required Field it must be Non-Empty";
            if(saddresstype=='')
                ErrorText+="\n        Address Type is Required Field it must be Non-Empty";
            if(scity!=''&&(!rcity.test(scity)))
                ErrorText+="\n        City allows only Alphabets";
            if(sstate!=''&&(!rstate.test(sstate)))
                ErrorText+="\n        State allows only Alphabets";
            if(scountry!=''&&(!rcountry.test(scountry)))
                ErrorText+="\n        Country allows only Alphabets";
            if (ErrorText!= "") {
                alert("Error :" + ErrorText);
                return false;
            }
            else{
                alert("success");
                return true;
            }
                
       }
    </script>

It show alert messages.I need disply the javascript validation messages below the input field.please giveme explanation with an example.