$sql="select usrid, concat(left(fname,1),lname) as username from loginuser order by fname;";
$result=mysql_query($sql)or die(mysql_error());

$sql="SELECT * FROM $tbl_name WHERE usrname ='$username' and pass='$pass'";
$result=mysql_query($sql)or die(mysql_error());

<?php
$host="localhost"; // Host name
$username=""; // Mysql username
$userpassword=""; // Mysql password
$db_name="test"; // Database name
$tbl_name="loginuser"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$userpassword")or die("Cannot connect to the Data Base");
mysql_select_db("$db_name")or die("Cannot select DB");

// username and password sent from form
$loginname=$_POST['loginname'];
$password=$_POST['password'];

// To protect MySQL injection
$loginname = stripslashes($loginname);
$password = stripslashes($password);
$loginname = mysql_real_escape_string($loginname);
$password = mysql_real_escape_string($password);
//echo "$loginname";
//echo "$password";
$sql="SELECT * FROM $tbl_name WHERE usrname ='$username' and pass='$pass'";
$result=mysql_query($sql)or die(mysql_error());
//echo "$result";
// Mysql_num_row is counting table row
$count=mysql_num_rows($result);
//echo "$count";
// If result matched $loginname and $password, table row must be 1 row

if($count==1){

// Register $loginname, $password and redirect to file "login_success.php"
session_register("txtLoginName");
session_register("txtPassWord");
header("location:./ff.php");

$sql="select concat(left(fname,1),lname) as username from loginuser;";

mysql> select * from loginuser;+-------+---------------+----------+---------+-----------+-----------+
| usrid | fname                   | lname        | usrname      | pass      | confpass  |
+-------+-------------------------+----------+-------------+-----------+-----------+
|   122 | vijay                          | ganesan  |                | vganesan  | vganesan  |
|   127 | sathish                      | durai        |                | sdurai        | sdurai    |
|   125 | selva                         | kumar      |                | skumar     | skumar    |
|   126 | rangith                       | fernando  |                | rfernando  | rfernando |
|   119 | madhusudhanan       | kannan   |                | mkannan    | mkannan   |
+-------+---------------+----------+---------+-----------+-----------+

<?php
$host="localhost"; // Host name
$username=""; // Mysql username
$userpassword=""; // Mysql password
$db_name="test"; // Database name
$tbl_name="userlogin"; // Table name

// Connect to server and select databse.
mysql_connect("$host", "$username", "$userpassword")or die("Cannot connect to the Data Base");
mysql_select_db("$db_name")or die("Cannot select DB");

// username and password sent from form
$loginname=$_POST['txtLoginName'];
$password=$_POST['txtPassWord'];

// To protect MySQL injection
$loginname = stripslashes($loginname);
$password = stripslashes($password);
$enpassword = stripslashes($enpassword);
$loginname = mysql_real_escape_string($loginname);
$password = mysql_real_escape_string($password);
$enpassword = mysql_real_escape_string($enpassword);

$sql = mysql_query("SELECT COUNT(*) AS total,username FROM loginuser WHERE username = '$username' AND password = '$password' GROUP BY username,id ORDER BY id, LIMIT 1")or die(mysql_error());  
$row = mysql_fetch_array($sql);  
if($row['total'] == 1){  

//login  
header("location:./login_success.php");
}  
else{  
echo "Wrong Username or Password";  
}  
?>