title: How to make the annoying 1px border that appears between the table border and table background and lets the page background show through disappear?
body: <p>A 1px "border" appears inside the border that is basically the page background showing even though there is a set background color for the table. It appears basically right next to the border.</p>
  
  <p>I have tried increasing the width of the border hoping it would cover it.</p>
  
  <p>Here is what it looks like on my end: [what it looks like on my end][1]</p>
  
  <p>Here is my css file and after it the function I want to use it in:</p>
  
  <pre><code>    width: 1000px;
      margin-left: auto;
      margin-right: auto;
  }       
  #title{
      height: 250px;
      width: 996px;
      border: 2px solid #0000ff;
      margin-left: auto;
      margin-right: auto;
      background-color: #55ff55;
      text-align: center;
  }
  #lefty{
      height: 600px;
      width: 246px;
      border: 2px solid #ff0000;
      margin-right: auto;
      background-color: #ff5555;
      padding: 10px;
  }
  #righty{
      height: 600px;
      width: 706px;
      border: 2px solid #00ff00;
      margin-left: auto;
      margin-top: -624px;
      background-color: #5555ff;
      padding: 10px;
  }
  .menu{
      display: block;
      height : 20px;
      width: 236px;
      text-align: center;
      font-size: 14px;
      font-weight: bold;
      color: black;
      background-color: #bb0000;
      text-decoration: none;
  }
  .menu:hover{
      color: white;
      background-color: red;
  }
  
  table, td, th{
      border: 3px solid black;
  }
  table{
      border-collapse: collapse;
  }
  }
  
  function MenutIr($x)
      {
          echo '&lt;table align="center"&gt;';
          foreach($x as $index =&gt; $ertek)  
          {       
          echo '&lt;tr&gt;&lt;td&gt;'; 
          echo '&lt;a href=?menu='.$index.' class ="menu"&gt;'.$ertek.'&lt;/a&gt;';
          echo '&lt;/td&gt;&lt;/tr&gt;';
          }
          echo '&lt;/table&gt;';
      }
  
  EDIT: I couldn't make the snippet work but here is a working version of it:
  &lt;?php
  session_start();
  ?&gt;
  &lt;!DOCTYPE&gt;
  &lt;html&gt;
  &lt;html lang = "hu"&gt;
      &lt;head&gt;
          &lt;title&gt; &lt;/title&gt;
          &lt;meta charset = "UTF-8"&gt;
          &lt;style&gt;body{
      width: 1000px;
      margin-left: auto;
      margin-right: auto;
  }       
  #title{
      height: 250px;
      width: 996px;
      border: 2px solid #0000ff;
      margin-left: auto;
      margin-right: auto;
      background-color: #55ff55;
      text-align: center;
  }
  #lefty{
      height: 600px;
      width: 246px;
      border: 2px solid #ff0000;
      margin-right: auto;
      background-color: #ff5555;
      padding: 10px;
  }
  #righty{
      height: 600px;
      width: 706px;
      border: 2px solid #00ff00;
      margin-left: auto;
      margin-top: -624px;
      background-color: #5555ff;
      padding: 10px;
  }
  .menu{
      display: block;
      height : 20px;
      width: 236px;
      text-align: center;
      font-size: 14px;
      font-weight: bold;
      color: black;
      background-color: #bb0000;
      text-decoration: none;
  }
  .menu:hover{
      color: white;
      background-color: red;
  }
  
  table, td, th{
      border: 3px solid black;
  }
  table{
      border-collapse: collapse;
  }
  }&lt;/style&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;?php
          $menu[1] = "Beolvas";
          $menu[2] = "Tényező";
          $menu[3] = "Oszt";
          ?&gt;
  &lt;?php
      function Debug($x)
      {
          echo '&lt;pre&gt;';
          print_r($x);
          echo '&lt;/pre&gt;';      
      }
      function MenutIr($x)
      {
          echo '&lt;table align="center"&gt;';
  
          /*
          vegigmegy a tombon a 
          beirt indexek sorrendje szerint
          index - index
          ertek - a tombben hasznalt ertek        
          */
          foreach($x as $index =&gt; $ertek)  
          {       
          /*
          table row, table data - minden elemet kulon sorban jelenit meg
          */
          echo '&lt;tr&gt;&lt;td&gt;'; 
          echo '&lt;a href=?menu='.$index.' class ="menu"&gt;'.$ertek.'&lt;/a&gt;';
          echo '&lt;/td&gt;&lt;/tr&gt;';
          }
          echo '&lt;/table&gt;';
      }
  
      function Olvas(&amp;$a)
      {
          if(!isset($_POST["a"]) || $_POST["a"]==""|| !is_numeric($_POST["a"]))
          {
              /*Urlap*/
              echo '&lt;form name="Olvas" action="" method="post"&gt;';
              echo 'a = ';        
              echo '&lt;input name="a" type="number" min ="1" size="3"&lt;br&gt;&lt;br&gt;';
              echo '&lt;input name="gomb" type="submit" value="Mehet"&gt;';
              echo '&lt;/form&gt;';
              return 0;
          }
          else
          {
  
              $a = $_POST["a"];
              $_SESSION["a"] = $a;
              return 1;
          }
      }
      function Oszt($a)
      {
          $d=1;
          for($d=1; $d &lt;= $a; $d++)
          {
              if($a%$d==0)
              {
                  echo "$d ";
              }
          }
      }
  
      function Tenyezo($a)
      {
          $d=2;
          echo '&lt;table&gt;';
          while($a&gt;1)
          {
              if($a%$d==0)
              {   
                  echo '&lt;tr&gt;&lt;td style= "text-align:right; border-left-style:hidden; border-top-style:hidden; border-bottom-style:hidden;"&gt;'.$a.'&lt;/td&gt;&lt;td style= "text-align:left; border-right-style:hidden; border-top-style:hidden; border-bottom-style:hidden;"&gt;'.$d.'&lt;/td&gt;&lt;/tr&gt;';        
                  $a = $a/$d;
              }
              else
              {
                  $d++;
              }
          }
          echo '&lt;tr&gt;&lt;td style= "text-align:right; border-left-style:hidden; border-top-style:hidden; border-bottom-style:hidden;"&gt;1&lt;/td&gt;&lt;td style= "text-align:left; border-right-style:hidden; border-top-style:hidden; border-bottom-style:hidden;"&gt;&lt;/td&gt;&lt;/tr&gt;';        
          echo '&lt;/table&gt;';
      }
  ?&gt;
          &lt;div id = "title"&gt; Php kezdetek &lt;/div&gt;
          &lt;div id = "lefty"&gt; 
              &lt;?php
                  MenutIr($menu);
              ?&gt;  
          &lt;/div&gt;
          &lt;div id = "righty"&gt;
              &lt;?php
  
              /*ha nem volt kattintas a menure*/
              $a = 0;
              $b = 0;
              if(!isset($_GET["menu"]))
              {           
                  Debug($menu);
              }
              else
              {
                  switch($_GET["menu"])
                  {
                      case 1: //kattintas az elso mezon
                          echo $menu[1].'&lt;br&gt;';
                          if(Olvas($a))
                          {
                              echo "a=$a&lt;br&gt;";
                          }
                          break;
                      case 2: //kattintas a masodik mezon
                          echo $menu[2].'&lt;br&gt;';
                          if(!isset($_SESSION["a"]))
                          {
                              echo "Nincs mit osszeadni&lt;br&gt;";                     
                          }
                          else
                          {
                              $a=$_SESSION["a"];                      
                              Tenyezo($a);
                          }
                          break;
                      case 3: //kattintas a harmadik mezon
                          echo $menu[3].'&lt;br&gt;';
                          if(!isset($_SESSION["a"]))
                          {
                              echo "Nincs mit osszeadni&lt;br&gt;";                     
                          }
                          else
                          {
                              $a=$_SESSION["a"];                      
                              Oszt($a);
                          }
                          break;  
                      case 4: //kattintas a harmadik mezon
                          echo $menu[4].'&lt;br&gt;';
                          break;
                  }
              }
              ?&gt;              
          &lt;/div&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  
  
    [1]: https://i.stack.imgur.com/3Ki0v.png
  </code></pre>