Rippling is a type of editing that moves all clips along if you insert another clip before it in the timeline. This also means that if you trim a clip, all affected clips will move along to fill the space created. By default, iMovie ripples clips.

To temporarily stop rippling from happening, hold down the Command key while doing an edit. This will stop all other clips from moving, so any gap you create in the timeline will appear as blank space.

If you want to extend a clip and trim the next one along, you can do this in one process by disabling rippling. Hold down the Command key and drag one clip over the next one along. Normally this would push the next clip along, but with rippling disabled, it overwrites that portion of the underlying clip.

Here is a tip I discovered on TUAW. To quickly go to the display, audio and keyboard preferences, you can hold down the option key and press the relevant F-key.

On a laptop the use is printed on the keys - keyboard brightness, sound volume and display brightness. On a desktop however, the only keys that show you what they do are the volume settings. F14 and F15 control the display contrast, so pressing Option-F14 (or F15) will take you to the display preferences. Of course desktops don't have backlit keyboards, so you can't do that one.

Sleep, Restart and Shut Down also have their own keyboard shortcuts. To put your computer to sleep, press Option-Command-Eject. To Restart, press Control-Command-Eject. To Shut Down, press Control-Option-Command-Eject. These are obviously very complicated to make sure you don't accidently press them whilst doing something else.

Here's a simple tip that I thought everyone knew, but apparently not. To switch between applications you can press Command-Tab. This fairly simple keyboard shortcut will switch from the current application to the last one used.

This isn't everything though. Continue to hold down the Command key after releasing tab, and the icons of all your applications appear across the middle of your screen. Press tab again whilst still holding Command and you can cycle through all open applications.

But there's more! Whilst still holding the command key, pressing Q will quit the hilghlighted application, and the list of open applications will remain active. Now you can use tab to move along the list and hitting Q will quit further applications.

Likewise this can be used with H to hide applications, and ~ to cycle through in the reverse direction.

Thats Application switching sorted, but a small development of this is a keyboard shortcut for window switching. This is less known about, and it involves pressing Command-~ (tilde) whilst in an application with multiple windows open. It doesn't bring up the screen display of open windows, but merely cycles through all open ones.

I find these shortcuts are sometimes a faster and easier alternative to the F9 and F10 of Exposé.

With Mac OS X Panther came the Finder Sidebar - allowing quick access to drives, files folders etc. Even though this is useful, it can sometimes take up a lot of space, especially if you have a small screen.

Some people will choose to disable the sidebar completely by double-clicking on the divider turning off the toolbar completely (command-option-T) if they want to save space, but there is another option.

You can drag the divider bar until only the icon shows, there should be a point where the bar jumps into place. Now don't worry that you can't tell what the icons are, because putting your cursor over any of them brings up the name. If you still want a way to distinguish between them, try adding custom icons for each item.

Here's a few tips and tricks for Microsoft Excel.

To insert the date as a time stamp (i.e. it won't change next time you change the document) press Control-Semicolon ( ; ). To insert the time, press Control-Shift-Semicolon. If you want a date and time that updates, type

=NOW()

into a cell.

Here's a quick way of making pop-up menus: Enter the pop-up choices into a series of out of the way cells. For example Oranges, Apples, Lemons, Pears into K1 to K4. Click on the cell you want the pop-up menu in, and in the Data menus choose Validation. Click on the Settings tab and choose List from the Allow pop-up menu. In the Source box that appears, enter your data range For example,

=J1:J4

and click OK.

To tidy things up, select cells J1 to J4 and choose a white text colour to make them invisible.

You want to learn another Excel tip? You can now have a tool that will convert PDF to Excel. This type of PDF converter is the newest PDF technology which allows you to easily edit your PDF documents again. You should also try a PDF to DOC converter for your Word Documents as well.

So you've discovered the joys of tabbed browsing. Now how do you quickly cycle through open tabs?

In Safari and Firefox this is a piece of cake. Pressing Command-Shift-Left Arrow (or Right Arrow) in Safari will cycle through all your open tabs.

In Firefox its Command-1 through to Command-9, for the first nine tabs at least. Confusingly these are the same shortcuts Safari uses for the first nine bookmarks. If you have more than nine tabs open, Control-Page Up and Control-Page Down Will let you scroll through them.

Apple offers a great page of iDVD Hot Tips at http://www.apple.com/support/idvd/hottips/

Apple offers a great page of iWeb Hot Tips at http://www.apple.com/support/iweb/hottips/

Apple offers a great page of GarageBand Hot Tips at http://www.apple.com/support/garageband/hottips/