Some ideas.

When a admin goes through the list and if he rejects a site then the site is just removed from the wcddl_wait but no email message or anything is sent to the Webmaster. No record is made anywhere so your just going to have that webmaster return and request to be whitelisted again and again.

Maybe you could add another column (int) 1 where 1 is processed and the site was rejected and 0 (the default) is still to be processed. That way if a Webmaster returns and tries to get whitelisted again they can be told that they are rejected. Other alternative is to have the code update the blacklist with a rejected reason. That means you'll have to add an extra input field in the form in the Webmaster area to give a reason.

I don't understand the reason behind this line:
$htmlsaida = 'For security reasons must check the box after the Site Url';
Why are you making them check the box? Can't you just add it as a hidden input like the email?

For safety you should also validate the email and surl again in the Admin area. If someone were to gain access to the admin area they could gain access to the server. Always validate everything everywhere.

You have the line where it's added to the whitelist commented out. I'm guessing that was for testing. You'll need to uncomment it now or else it won't work for people.

No reason for `type1` to be TEXT. It can be VARCHAR( 10 ) NOT NULL like the other type2 and type3.

You could expand on this a lot more but it's a good start.