In your recent Firefox review, you said Internet Explorer has a private browsing mode that doesn’t record your history or tracks while surfing. But I can’t find how to turn it on.

The feature, which is called InPrivate Browsing, is only available in the latest version of IE, called IE8. You turn it on by either selecting that option from the Safety button at the upper right, or from the Tools menu in the Menu Bar if you have chosen to make that bar visible. Once you do, an “InPrivate” label appears at the top left corner of the browser and a page appears explaining that the browser won’t record on your own PC certain records of what you do in that browsing session. There’s an additional privacy mode, available from the same two drop-down menus, called “InPrivate Filtering,” which goes further. It blocks Web sites you go to from saving certain records of your presence there on their own servers. InPrivate browsing lasts until you close the InPrivate browsing window.

When you reviewed the latest Safari Web browser awhile back, you complained that Apple had repositioned the tabs in a way that made them harder to see. A friend said that’s no longer true. Is he right?

Yes. After getting a lot of negative reaction, Apple changed Safari 4’s design so the tabs are displayed in the previous manner, below the toolbar, instead of at the very top. The company also made more visible the page-loading indicator, though I personally still prefer the indicator style used in prior versions.

In your column last week, you recommended add-on software to search documents for key words in Windows XP. Is there any similar software that will do the same for Macs?

It’s unnecessary on Mac because the Mac operating system comes with a fast, comprehensive search system called Spotlight that’s built right in. Windows Vista also has a very good search system built in. The reason I recommended add-on software for Windows XP is that I consider XP’s built-in search to be slow and inferior to those in these two newer operating systems.

You can find Mossberg’s Mailbox, and my other columns, online for free at the All Things Digital Web site, http://walt.allthingsd.com.

Last week, when you wrote about the ChaCha cellphone search service, you didn’t say how they make money. Are they collecting phone numbers from customers so they can send spam text messages, or sell the numbers to others who will do so?

ChaCha allows you to ask any Web-searchable question, by speaking it or texting it over a mobile phone, and then it sends you the answer via text message. The company charges consumers nothing, but says it is hoping to make money by striking deals with cellphone carriers to incorporate the ChaCha service into their current 411 phone-number look-up services. Also, it hopes to eventually include ads in the text message answers it provides.

In addition to the message that includes the answer, ChaCha sends you a message saying it is working on your request and restating your question, so you can see if it understood you correctly. It also sends an introductory text message to first-time users and occasional tips on how to use the service. Scott Jones, ChaCha’s chief executive, asserts that “we do not spam” and “we never make phone numbers and/or email addresses available to others.” He said the company is updating its privacy policy to make that clearer.

We have DSL service. I use several Web-based applications, one of which is online backup, and my husband is concerned that they degrade his use of the Web, which includes creating Web sites. I contend that that is like saying turning on one light bulb is using too much electricity, that two people on one DSL line aren’t using up too much bandwidth. Who is right?

Every situation differs, depending on exactly which programs you are each using, how you have them set, whether you are using them simultaneously, and how fast your DSL connection is. However, in general, your husband is correct that it is possible for heavy Internet usage on one computer in a home to slow down Internet speeds on another.

This is especially true with something like online backup, because it relies on your DSL account’s upload speed, which is typically far slower than the download speed. If your online backup program is trying to push a bunch of files over a slow upload connection, while he is in another room trying to upload new versions of a Web site over the same narrow upload pipe, it could affect the speeds he gets. You might try coordinating or staggering those online activities that involve heavy uploading. Normal Web surfing or emailing shouldn’t require any such coordination.

I am thinking about purchasing a Dell (DELL) XPS One all-in-one desktop, but I have one question. Does the Dell’s built-in TV tuner require any extra attachments to watch TV right out of the box?

You can watch over-the-air stations and analog basic cable stations right out of the box, without added equipment. However, you may want to connect a small desktop antenna to improve reception, which is what I did when I tested this machine. To use the XPS One with digital or premium cable or satellite stations, you would have to connect it to a cable or satellite receiver, just as most people do with their TV sets. This requires the use of an adapter that comes with the machine.

• You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital web site, http://walt.allthingsd.com.