That's a shame Yana as you have a great product but almost no website today is HTML valid. Most designers use templates from places like RocketTheme and JoomlaXTC and none are 100% HTML valid.
For instance, your own "Features" page registered 13 errors on validation!
You need to make your product more forgiving for Internet Exploiter as there are dozens and dozens of us who would be glad to buy your extensions except they do not work in Internet Exploiter!
Goodbye and good luck as I will have to use a different, more forgiving solution!