[Vince]

I don't recommend writing your own panel if you have no experience.

• $_POST['username'] is not a safe string. Don't use it directly in a query. A user could basically supply anything here, possibly corrupting the query.
• Don't use the 'mysql' module; it's deprecated. Use mysqli or PDO instead.
• The <center> tag is deprecated, as is the <font> tag (since 1999, no less). Use CSS for styling.