The function to delete the selected page (or pages) from a PDF file disappeared from the Edit menu of Preview in Snow Leopard. Even worse, it was replaced (using the same Command-Delete shortcut) with a command that moves the entire PDF document to the trash.

You can, however, still delete selected page(s) through an undocumented keyboard shortcut. Hold down Shift-Command-Delete with one or more pages selected, and only those pages will be deleted from the document. Page numbering, however, does not update to reflect this deletion until you (re)save the file (in 10.5, the numbering updated instantly upon deletion).

If you have a laptop that supports multitouch gestures, you probably are aware of the fact that a three-finger swipe in Preview will go to the next or previous page in a PDF. But you may be annoyed at how Preview insists on animating each page switch with a small scrolling action. This can make it very slow to scroll through a document -- almost as slow as regular two-finger scrolling.

Fortunately, there is a solution: use a three-finger swipe in the sidebar. When you swipe in the sidebar, the pages will change instantly, without any animation. This works no matter what mode the sidebar is in (table of contents or thumbnails). And if you are in contact sheet mode, three-finger swiping will navigate you through the contact sheet.

I can only test this in 10.6, and I didn't discover it until I was running 10.6, so I don't know if it works in 10.5 or not.

[robg adds: My MBP is also 10.6-only now, so I can't test in 10.5 either. If you can, please post in the comments.]

Locating an email message in your Mail folder hierarchy is now a snap. As of Snow Leopard's version of Mail, if you open a message in a new window, Command-clicking (or Control-clicking) on the icon in the title bar of the message window will reveal the path to the enclosing folder for the message (just like it does in the Finder).

Select the folder from the drop-down menu, and it will open in a new Mail browser window. This allows you to easily locate the message within the Mail folder hierarchy, which can prove quite handy.

Viewing Microsoft Entourage email messages in the Finder with Quick Look doesn't work -- it merely displays an icon image. If you have Entourage 2008 and 10.5 or 10.6, there is a way to display the contents of the message in Quick Look. Download the file named Entourage QuickLook Plug-In.dmg from this site, and place a copy in the /Library/QuickLook folder.

This solution is especially useful for scrolling through Spotlight search results in the Finder, with Quick Look opened in full screen mode on a second monitor.

[robg adds: The plug-in should also work in your user's Library/QuickLook folder. I don't use Entourage, though, so I can't test this one.]

To use the old-style contextual menus when you click-and-hold on an application's icon in the Dock (i.e. how it worked in 10.5 and earlier), type the following two commands in Terminal (don't type the $):

defaults write com.apple.dock show-expose-menus -bool no; killall Dock

All credit for this hint goes to Jeff Johnson of Lap Cat Software, who blogged about the solution. This hint is a significant update to this one, which pointed out you can use Control-click to get the old-style contextual menus.

[robg adds: To undo this behavior, you can either change no to yes in the above command, or delete the key entirely with defaults delete com.apple.dock show-expose-menus; killall Dock.]

Not a big of the yellow background in Apple's Mail.app Notes? Handy with a text editor? You can change the background with a few simple steps. First, make a backup of your Mail application in case something goes wrong.

With the backup in place, Control-click on Mail.app and choose Show Package Contents from the pop-up menu, then navigate into the Resources folder. Using BBEdit (or another plain text editor), open the following three files: note-view.html, note-window.html, and note.css.

In the two .html files, locate the img tag that references note-background-gradient, and delete the entire line (or comment it out with the <!-- --> tag pair). In the .css file, change the background:rgb values to something pleasing; I used 250, 250, 245 so it would look nice with the rest of the Mail motif.

Save the edited files and launch Mail, and enjoy your non-yellow Notes.

[robg adds: Note that this edit will break code signing on Mail (in 10.5 and 10.6); you can check this yourself in Terminal with the modified app:

$ codesign -v /Applications/Mail.app
/Applications/Mail copy.app: a sealed resource is missing or invalid

However, I'm not sure what impact this may have, at least in 10.5. I tested this hint and then used my modified Mail app to check and send email without any troubles. I'd suggest, however, making the changes on a duplicate version of Mail and leaving the original untouched. Run the modified duplicate instead of the original, and then you can easily switch back if you have any problems.]

As someone responsible for supporting Macs, I carry around an external drive (LaCie Rugged with USB2, FW400, and FW800 connectors) that holds all my tools, as well as different versions of OS X, reaching from 10.3 (PowerPC) to 10.5. Recently, I had the time to finally add a 10.6 partition to the drive, and noticed that Snow Leopard won't install on a non-GUID drive -- the Installer simply won't let you continue.

I can't afford to loose the ability to boot PowerPC systems like 10.3 or 10.4 or even the universal 10.5, so repartitioning as GUID was not an option here. Knowing that Intel versions of OS X will boot just fine (though officially unsupported) on APM-formatted drives, I solved this in a somewhat inelegant but effective way: I installed 10.6 on another drive with the GUID partition scheme, and simply cloned it back to an empty partition on my APM drive.

So for now, at least, I can still use one drive to boot all these systems: 10.3 PowerPC, 10.4 PowerPC, 10.4 Intel, 10.5 (Universal), 10.6 (Intel only, of course). Note that this might change in the future (10.7?), but for now, it works fine.

The latest version of the iPhone OS allows you to have 11 pages of 16 icons, plus the four permanent icons at the bottom of the screen, for a total of 180 apps. You can actually have more than 180, though only 180 icons will be visible.

To get to the invisible apps, just do a search (press Home from the home screen), and type part of the non-visible app's name. I don't know how many of these invisible apps you can have, as I have not tried more than three so far.

[robg adds: As far as I know, the limit is simply based on the available space on your device. Long before that point, though, you may run into a limit with your ability to remember the names of all the invisible apps.]

After upgrading from 10.5.8 to 10.6.1 on my MacBook Pro, I was unable to connect to wireless networks unless I had already connected to them running under 10.5.8. Snow Leopard would "see" the new networks, but could not connect to them.

The Genius Bar at the Apple Store helped me solve the problem. We opened Library » Preferences » SystemConfiguration, and trashed the entire contents of that folder. We also deleted all locations in System Preferences » Network, and recreated the location Automatic. Finally, we rebooted.

So far, I have been able to connect to all wireless networks that I want to using OS X 10.6.1.

One of the "features" in Apple's Mail program that has always annoyed me is how it handles messages after doing a delete operation. If you press Delete to throw away the message you're currently looking at, Mail displays the next message (marking it read in the process). While I like the fact that Mail marks displayed messages as read, I have always found it annoying that it displays a message that I have not specifically selected (and then marks it as read).

There's a way around this. Instead of pressing Delete, press Option-Delete. With this shortcut (which doesn't show up in the Edit menu), Mail deletes the currently-displayed message and then does nothing at all, and the next message is not displayed. This is exactly what I want -- I now must explicitly tell Mail when I want a message to be displayed.

I expect I can make this the default using the Keyboard Shortcuts tab in the Keyboard System Preferences panel, but I have yet to play with that.

[robg adds: It doesn't appear you can change the shortcut for Delete to Option-Delete, because OS X won't let you use the Delete key as part of a shortcut.]