let say I have a post that can be found on page post.php?pid=60 but if the user changes the url to post.php?pid=95 the page is displayed all weird is 
there a way I can have them redirected to another page that says post dosn't exist or something? If so how would I do this? And is this the best way to handle none existent pages? If not what is preferred?
I'm using PHP & MySQL if that helps.