You are going to have a hard time attracting serious web designers until your site implements valid XHTML and modern web standards. For starters, run it through a validator such as the one provided by W3C and fix the numerous warnings and errors. Next work on
separation of presentation and content. Most professional designers take this topic seriously (and the ones that don't should!). You can start by ripping out the inline styling and icky presentational tags and attributes (font, and the width, height, etc. attributes) and replacing them with some clean semantic ids or class names, then handling your styling in a linked stylesheet (or a couple separated by function, many designers like to use one for position, one for color and decoration, and one for typography for instance). Trust me, when you go to change your design the first time and you can do it all in one place instead of digging through thousands of lines of code in disparate php files you will thank yourself.
As for design sense, that's really something that comes from developing your artistic taste and ability, but a solid understanding of color theory and the art of UI design is a great way to both build your skill and find inspiration. If you can afford to buy a book I highly recommend
Transcending CSS by Andy Clarke, which is also available on
Safari Books Online (if you haven't heard of Safari, it's like the computer books section of Barnes and Noble on steroids, with access to up to 10 books at a time for 20 bucks a month or unlimited access for 30 and great discounts on buying physical copies, it's an *amazing* resource).
Sitepoint also published a book recently on the subject of design theory, I can't recall the name atm but it's worth a read particularly for its chapter on typography.
You may also consider recruiting an artistic friend to help you do some designing, designer/developer teams are a great marriage of skills. Just have him do mockups of what he would make the site look like in the graphics app of his choice and provide input on what sorts of things you're comfortable with implementing. You will find that this is very common in the professional world so it's great practice if you're serious about getting into web design/development.
That's probably very overwhelming for a simple commentary but I believe in teaching people to fish. Good luck :D
