I have designed a CSS file after exploring it on the google about how to make a css file for produce multiple color in the table data.
I added this CSS file in my php file but it's not working, i don't know why.

Please find my code below.

My Php file

Code:
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>CHP Search Incidents</title>
<link href="design.css"  type="text/css" rel="stylesheet" />
</style>
</head>

<body>
<p>MM/DD/YYYY</p><form action="" method="POST">
<input type=text name=search >
<input type=submit name=submit value=Search>

</form>
</body>
</html>

<?php
   
   $date=date("m/d/Y");
   echo "Today Date Is = ";
   echo "$date";

   include("connection.php");
   $table="baltimore";
   

   if(isset($_POST['submit']))

   {


	$selectcondition = "SELECT * FROM order_details where DATE='".$_POST['search']."'"; //Select Query Which check the INCIDENT ID whether the TURNOVER for the given INCIDENT is exit or not.

	$check=mysql_query($selectcondition,$con);
	$fetch=mysql_fetch_row($check); 


		if(!$fetch)            				//If checklist for the given date is not exit execute if condition 

		{


	                echo "<font color='red'>";
			echo "<br>";
			echo "No Order Found In The Database"; 
			echo "<br>";
	                echo "</font>";

		}
	
		 else //if the above condition is flase !
     
	     	 {
     
		 	$sql= "select * from order_details where DATE='".$_POST['search']."'";
         	

	         	$mydata=mysql_query($sql,$con);
			//$fetch_rows=mysql_fetch_row($mydata);
		
			 echo "<table width='100%' height='10%' border='1' cellspacing='0'>
              
				 <tr  bgcolor='#FF6600'>
		                  <th>MODIFIED DATE</th>
		                  <th>Sample ID</th>
		                  <th>ORDER</th>
		                  <th>STATUS</th>
						  <th>DESCRIPTION</th>
			              
              		 </tr>";
			
			while($records = mysql_fetch_array($mydata))
         
		 	{
			
	            	echo "<tr class='mytable'>";
	            		echo "<td>" . $records['TIMESTAMPS'] . "&nbsp;</td>";
	            		echo "<td>" . $records['SAMPLEID']. "&nbsp;</td>";
	            		echo "<td>" . $records['ORDER'] . "&nbsp;</td>";
	            		echo "<td>" . $records['STATUS'] . "&nbsp;</td>";
						echo "<td align='center'>";
						echo '<textarea  name="textarea" cols="100"  >'.$records['COMMENTS'].'</textarea><br>'; 
					echo "</td>";
		

	  		}
		
  				
			echo "</table>";
			
		
			
		}

}
?>
MY CSS file

Code:
@charset "utf-8";
/* CSS Document */

.mytable {
	width:100%;
	border-collapse:collapse;
}

.mytable td {
	padding::8px;border:#999 1px solid;
}
	
.myTable tr:nth-child(even) { /*(even) or (2n+0)*/
background: #A4D1FF;
}

.myTable tr:nth-child(odd) { /*(odd) or (2n+1)*/
background: #EAF4FF;
}
Please guys do reply me ASAP.

Thanks alot in advance.