Menu showing too much; missing page

Sorry to hit y'all with another problem so quick... and actually it's two problems.

First, my customer will be selling t-shirts. I have set up eleven main categories, representing the lines of t-shirt designs.

I have made sub-categories that represent each design in a category/line.

If you hover over a category name, the menu will show the sub-categories in the correct place - as a 2nd level menu.

BUT... all of my subcategories are also appearing in the first submenu level at the end of the list of main categories.

The site is index.php (I have a placeholder page [default.htm] that will show if you don't type in index.php).

So that you can quickly find the error, highlight "Celestial", and you will see "Sun Moon & Stars" "Half Sun/Moon" and "Got It Made" on the submenu, but you will also see those same three designs listed in the main categories. Same goes for any other sub-category I set up.

Did I do something wrong, or is this how the menu works?

SECOND PROBLEM: I have set up a product that has advanced options for sizes. This product is under the category "Mojo Man" and is the Mojo Man Head Shot. If you click on Mojo Man Head Shot (in submenu 2), it takes you to products_details.php, which gives a 404 - File or Directory not found error. I notice that my site does not even have a file named "products_details.php". There is a products_detail.php, though.

Thank you in advance for your patience & help!

~Fergie