Does anyone know if there´s a shortcut to switch between tabs in Google Spreadsheets?
If you use CTRL+PgUp / CTRL+PgDown like in Excel you switch between Chrome or Firefox's tabs instead.
Use the following short cuts:
Ctrl + Shift + PageDown ==> Move to next sheet (Cmd + Shift + Fn + Down arrow on a Mac)
Ctrl + Shift + PageUp ==> Move to previous sheet (Cmd + Shift + Fn + Up arrow on a Mac)
See reference: Keyboard Accelerators