No Trackpad on the PowerBook 150 according to Apple. Apparently a popular weekly paper publication slipped up and incorrectly stated that the new entry-level notebook computer sports one of the touch-sensitive devices found on the 500-series PowerBook models. In fact, the 150 has the same rolling trackball found on most previous 100-series models. [MHA]
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).