To be honest mate - I don't even know where to start...

Please consider everything I say to be constructive criticism, not a personal attack.. I don't like to sugar coat what I say, people tend to miss the point when you try to be nice

When I first visited your site, I had no idea what it was offering, and more importantly, why I would be interested in staying on there to learn more. It's difficult to read text on product pages as it is centered (good for parts of some pages... TERRIBLE to read paragraphs.). I'd suggest going back to the drawing board a bit there!

Now.. on from that, let's go through your questions..

1) Probably OK - I don't know what the demand is, but I'm sure there are enough people that would want to learn about banner ads, creating banner ads, advertising networks, etc...
2) Fix the site - it's painful at the moment. Aside from that.. create some helpful articles and rank them. Add affiliate links in the articles to useful products that relate to the content of the article (eg. Photoshop, WP plugins, etc..) Also.. why on earth are you using ClickBank for your payment processing? The item value is far too low for any affiliates to be interested, and it's very expensive compared to other methods... Just use PayPal and be done with it!
3) No. You don't have enough content to rank for anything that I can see.. aside from that, you've got a couple of backlinks that are OK.. without content you can't really rank for anything though.Permalink structure should be changed to site.com/page, rather than site.com/?page=page.
4) Personally it's not to my taste.. I'm definitely not the right person to comment on design though

Also, trying to get people to complete a PPI/PPD offer is probably going to leave a bitter taste in their mouths once they start getting popups wherever they browse.. I think most people are VERY wary of this nowadays.. If you MUST go down that path, it might be better to package a useful program with PPI/PPD and offer it as a free download for them, but not make it mandatory. I don't think you'll have loyal customers if you do this sort of nonsense though.

Again - don't take this as an attack on you personally.. I just think you may want to take a big step back and develop a bit more of a plan..

1) Figure out what it is you want the site to do
2) Figure out the most cost effective way to do this
3) Determine if it's profitable enough
4) If it is, do it! If not.. find something else!

Cheers,
Michael

Just had another look - and I get the impression you're trying to revinent the wheel a bit..

Whatever software your using to create the shop/website.. throw it away and use something else (eg. WordPress). It's doing bizarre, bad stuff that should never be done...

eg. product pages are only available by performing a POST to shop.php.

This is plain messed up - it means:

1) Search engines will NEVER be able to see your product pages...
2) People CANNOT pass links around for the pages
3) You can't link to pages if you wanted to in most places (eg. you can't post a link to a product on WF)
4) Even if you can control HTML somewhere - creating a link is HARD. (you'd need to create a form and submit it via JS, or a submit input.. or something)

Cheers,
Michael

Hey dude your website is not working, you have problems with server. Try to set the issue so people can see what is about.

Oh, I can't visit your site mate.

There's certainly a lot of room for improvement. Michael made a lot of great suggestions, you can start with those. I agree with what he said too. Before you proceed with the makeover, determine what the purpose of the site is. What is your aim in creating it? Knowing what the goal is will help move you forward as you make the modifications.

Good luck!