Q. I downloaded a program from a Web site to run on my Mac, but the system won't let me open and install it because of "security preferences." What is this and is there a way around it?
A. The default settings in the latest version of OS X (10.8) allow only programs from the Mac App Store (and what Apple calls identified developers) to be installed on the computer. The alert you see on the screen comes from Gatekeeper, one of the built-in OS X security features intended to protect the Mac from malicious software.
If you trust the source of the program and want to install it anyway, you can get around Gatekeeper in a couple of ways. To install a blocked program manually from the Mac's desktop, right-click (or hold down the Control key and click) the program's icon. In the drop-down menu that appears, choose Open and then click the Open button in the alert box to proceed with the installation.
If you install a lot of trusted software and want to relax the Gatekeeper security to save time and headaches, you can change the settings in the Mac's System Preferences. Either click the System Preferences icon in the Dock, or go to the Apple menu in the top left corner of the screen and choose System Preferences.
In the System Preferences box, click the Security & Privacy icon and then click the General tab. To change the settings, click the lock icon in the bottom corner of the box and type in your OS X account name and password. Next, under the "Allow applications downloaded from:" line, choose "Anywhere" and close the preferences box. If you want to tighten the security later, you can return to the Gatekeeper preferences and restore the stricter settings.
Improving Skype Call Quality
Q. I often find the audio quality of Skype calls to be pretty bad. Is there a way to make it better?
A. Among other things, Skype is at the mercy of the Internet's general traffic and congestion, but there are a few things you can try to improve the audio quality. If you are on a home network with the rest of the family, ask them not to download video, play online games or engage in other bandwidth-intensive activities during a call.
Using a headset microphone instead of the computer's built-in microphone and speakers can make for a better-sounding experience, too. Skype's Web site recommends several headsets from Plantronics and Logitech that are certified to work well with the service.
If possible, making Skype calls from a computer directly connected to the network with an Ethernet cable may help with the audio quality, as a weak Wi-Fi or cellular-data signal can result in lousy sound and dropped calls. If a wireless connection is the only option, try to position yourself near the router or a place where you can get a strong network signal.
Using older versions of the Skype software on either end of the call could also affect the audio quality. If you think you may be a version or two behind the program's current release, open Skype, go to the Help menu in Windows (or the Skype menu on the Mac) and choose Check for Updates. If a newer version is available, the program offers to download and install it for you. The people you call regularly should check their systems for updates as well.
This article originally appeared in The New York Times.