If a program or dialog box has tabs (different divided sections or pages with a label at the top), chances are that Ctrl+Page Up and Ctrl+Page Down will change tabs.
Try this out with Firefox and Excel to start off.
In Firefox, remember from yesterday that you can create a new tab with Ctrl+T. Now use Ctrl+Page Up to rotate through the pages (or Ctrl+Page Down to rotate the other way).
In Excel, you’ll start out with three sheets (Sheet1, Sheet2, Sheet3) when you start a new document. Ctrl+Page Down will move from Sheet1 to Sheet2 and Sheet2 to Sheet3. Ctrl+Page Up will move from Sheet3 to Sheet2 or Sheet2 to Sheet1.
For dialog boxes, if Ctrl+Page Up and Ctrl+Page Down don’t change tabs for you, try Ctrl+Left Arrow and Ctrl+Right Arrow, or Ctrl+Up Arrow and Ctrl+Down Arrow. Unfortunately, applications aren’t always as consistent as we’d like.