1st and 2nd level menus have entirely different feelings than 3rd level menus. As such, some people prefer using 3rd level menus in place of 1st and 2nd level menus. To accomplish this, a few tricks must be employed:
1) First create a 1st level, but don't put in a lot of content. Just fill out the required information, throw a character into the body, MAKE SURE THE PAGE IS VISIBLE, and then save.
2) Create a 2nd level page under the 1st, but don't put in a lot of content. Just fill out the required information, throw a character into the body, MAKE SURE THE PAGE IS HIDDEN, and then save.
3) Create a 3rd level page under the 2nd, and this time, put in all of the content you wish for the page to have. Save the page.
4) Go to Settings > Advanced > Redirect old pages to new pages > Add a new redirect
5) Type in the remaining part of the link for the 1st level menu in the Old Url field.
6) Type in the remaining part of the link for the 3rd level menu in the New Url field.
7) Save redirect.
Now, when people click that tab on your website, they will go to a page that has the 3rd level menu style instead of menus underneath the 1st level menu (2nd level menu style).
NOTE: You can create more pages under the 2nd page to increase the links shown in the 3rd level menu. You will not have to change the redirect Urls, unless you want a new page to show instead of the initial once created. In which case, redo step #6 with the new page link.