2 Very quick questions

[kows]

javascript can't do what you want to do.

I would say the best possibility is what I posted just above your post (not sure if you've seen it or not). For <select> and checkbox form fields, it will all depend on how you're building your form. Basically, for your <select>, you will do this:

Category: <select name="category">
<?php
  $i=0;
  while($i < $num){
    $catid=mysql_result($result,$i,"Catid");
    $catname=mysql_result($result, $i, "Catname");
    echo '<option value="$catid"';
    if(isset($_POST['category']) && $_POST['category'] == $catid))
      echo ' selected="selected"';
    echo '>' . $catname . '</option>';
    $i++;
  }
?>
</select>

edit: The htmlentities() function just converts HTML entities, like dobule quotes, ampersands (&) and other things like that, to XHTML compliant characters, like & quot; and & amp;. It will make sure that your inputs do not incorrectly "break" because someone entered a quote in their text.