how to open all links in one page

I have on my side bar links. I want when I click on each link to open each page in the same one, which is the blog.php. I tried, but I guess I'm missing something because doesn't work. I need a little help.
This is my code, with the blog.php, where I have the side bar:

<?php
        include ('mysql_connect.php');
		
        $query = "SELECT id, title, author,post,category, DATE_FORMAT(date, '%M %d, %Y') as sd  FROM news_posts ORDER BY date DESC";
        $result = @mysql_query($query); 
        if ($result) 
	{
          while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) 
	 {   
          $mess = stripslashes($row['post']); 
          echo '<p class="text"><b><a href="article.php?id='.$row['id'].'">'. $row['title'].'</a></b><br />'. $row['sd'].'<br />
		  Category: <b>'.$row['category'].'</b><br />
		  Posted by: <b>'.$row['author'].'</b><br />';
		  
          echo snippet($mess, 200, true);
          echo "</p>"; 
          }
        }  
	else 
	{  
          echo 'There are no news posts to display';
        } 
        ?>	
		
        </div>	
        <div id="sidebar">  
	   <div id="top_sidebar">								
           
          <?php
           $cat = $_GET['category'];
	   $query = "SELECT id, title, author,post,category FROM news_posts WHERE category='cat'";
	   $result = @mysql_query($query);
	   if ($result){
		$count_items = count($result);
		$cat = $row['category'];
                echo '<a href="blog.php?cat=css">CSS</a>';				
	    }  
			?>
		  </div>		
        </div>

PHP:

 

I'm not sure what exactly you are trying to do, but I think the problem is here -

<?php
$cat = $_GET['category'];
$query = "SELECT id, title, author,post,category FROM news_posts WHERE category='cat'";
$result = @mysql_query($query);
if ($result){
    $count_items = count($result);
    $cat = $row['category'];
    echo '<a href="blog.php?cat=css">CSS</a>';        
}  
?>

Code (markup):

This will only echo out one link multiple times (<a href="blog.php?cat=css">CSS</a>). Should it possibly be -

<?php
$cat = $_GET['category'];
$query = "SELECT id, title, author,post,category FROM news_posts";
$result = @mysql_query($query);
if ($result){
    $count_items = count($result);
    $cat = $row['category'];
    echo '<a href="blog.php?cat='.urlencode($cat).'">'.$cat.'</a>';        
}  
?>

Code (markup):