3.css

<!DOCTYPE html>
<html>
<head>
    <title>css</title>
    <link rel="stylesheet" href="style.css">
    <style>

b { font-size:17px;
background-color:#5f5f5f;
color:#f1f1f1;
}

    </style>

 </head>

    <b>This text is bold</b>

<table style="width:100%" border="1">
  <tr>
    <th>CSE</th>
    <th>BBA</th>
    <th>ENGLISH</th>
  </tr>
  <tr>
    <td>Sec A</td>
    <td>Sec A</td>
    <td>Sec A</td>
  </tr>
  <tr>
      <td>Sec B</td>
    <td>Sec B</td>
    <td>Sec B</td>
  </tr>
  <tr>
       <td>Sec C</td>
    <td>Sec C</td>
    <td>Sec C</td>
  </tr>
  <tr>
   <td>Sec D</td>
    <td>Sec D</td>
    <td>Sec D</td>

  </tr>


</table>


<p>  This is link  <a href="#">Click Here</a> </p>

    <!---- externel style.css--->

   body{
    font-family:Verdana,
    sans-serif;
    font-size:15px;
    line-height:1.5}


     <!---- externel css--->


</body>
</html>