>I have a question about the following design approach for web application which targets are tablet browsers like iPad, Nexus, etc. The approach I choose is the following:
>The main page of the application has a pull-down menu. When user clicks on an item of the menu a new tab is opened. For example, one of the items on the menu is View Order. And I envision that a user may want to see several orders at the same time. So when he/she clicks on this menu anchor, a new tab is opened where user enters order number and views the order. At the same time he/she can click on the same menu item again and open another tab to view another order. And so on. So practically, the main tab/page of the application will host the main menu and some static text (I have not come up with what text though).
>What do you think about this UI approach? Would this type of app be called MPA (Multiple Page Application) as opposed to SPA (Single Page Application)?

IMO you can go either MPA or SPA, whichever seems easier to the user to you. From what I have read the key to less than desktop UIs is to keep the crucial information there on the screen without scrolling. That means some stuff that would appear in a desktop window has to be dropped. I don't believe the one-size-fits-all approach works.