That is the question that Mozilla, the nonprofit organization that makes the leading alternative browser, hopes to answer this month when it releases version 3.0 of its Firefox Web browser. In some tech-industry circles, Firefox already is preferred over Microsoft’s (MSFT) Internet Explorer and Apple’s (AAPL) Safari, but it still isn’t used by most people, and Mozilla is hoping to broaden its appeal.

The new version will be released simultaneously for Windows and the Mac’s OS X operating system, as well as for Linux. While each of the three editions will have the visual style of the operating system on which it runs, all three will have the same features.

I’ve been using prerelease versions of Firefox 3.0 for months, and have recently been testing a near-final version and comparing it closely to IE and to Safari. I have tested it on multiple Windows PCs and Macs, on desktops and laptops, over slow connections and fast ones. I have tried it with well over 100 Web sites.

My verdict is that Firefox 3.0 is the best Web browser out there right now, and that it tops the current versions of both IE and Safari in features, speed and security. It is easy to install and easy to use, even for a mainstream, non-technical user. It can be downloaded, free, at mozilla.com by clicking on “Firefox 3 Sneak Peek.”

This situation may change. Microsoft is working on a new version of IE, scheduled to be unveiled later this year, with some impressive new features. And Apple is always working on new iterations of Safari, though it is secretive and hasn’t disclosed its plans. But for now, in my view, Firefox 3.0 rules on both Windows and Mac.

I couldn’t find any significant downsides to Firefox 3.0. Every page I tried rendered properly and rapidly on both platforms. I ran into only one glitch, in a preference setting. That problem appeared on only one of my four test machines and was fixable with the help of Mozilla, albeit via a geeky method.

In the one or two cases where Firefox lacked a feature I thought important, such as the “auto fill” feature in Safari that can quickly fill out an online form, I was able to find an add-on that did the trick from Mozilla’s vast library of add-ons, which are written by people all over the world. (One caution: Some existing add-ons won’t work with the new version until their authors update them.)

When Firefox first came out, it was the fastest browser, but it lost that title over the years. However, in my tests, this new third version of Firefox regained the speed crown. It beat IE 7 handily on my test Windows computers and edged Safari slightly on my test Macs.

For example, using a new Dell (DELL) XPS One desktop, I opened identical folders containing the same 16 bookmarks on both IE 7 and Firefox 3.0. IE took 37 seconds to completely display the 16 pages, but the new Firefox did it in just 23 seconds. On a new Apple iMac, I did a similar, but more daunting, test — opening identical folders containing 24 bookmarks. Safari rendered all of the pages in 36 seconds, but the new Firefox finished the job in 32 seconds.

The latest Firefox has a number of new and improved features. If you type any word or phrase into its address bar, the browser instantly searches your history and bookmarks for a possible match, to save you from typing or combing through your bookmark list.

The whole process of managing bookmarks has been vastly simplified. Every Web address is accompanied by a star icon at the right. To bookmark the site, you just click the star once. No other action is required. To specify where to file the bookmark, you click the star twice. You also can remove bookmarks by clicking the star. And you can tag bookmarks with key words, to make it easier to find them.

There are also smart bookmark folders, which gather your most visited sites, or most recently bookmarked sites, automatically into folders. You also now can more easily back up and restore your bookmarks, complete with tags.

Security is also improved. The old version of Firefox would warn you when a site you were visiting appeared to be a fake, designed to steal your identity. (IE has a similar feature, though Safari doesn’t.) But Firefox 3.0 now warns you about sites that are known for trying to plant viruses, spyware and other malicious software on your computer, a warning the other big browsers don’t yet provide.

With one click, Firefox 3.0 also provides details about who owns the site you’re visiting, and whether it’s encrypted, if the site owner has adopted a special type of security certificate.

My bottom line: Even though you already have a built-in browser, Firefox 3.0 can improve your Web experience.

• Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

In fact, your boring old cellphone has enormous potential. Here is a guide to checking your email, looking up information and updating your calendar, just by sending text messages. You can use any cellphone, but you’ll need a generous text-messaging plan.

For email, I tested TeleFlip, a free service that lets you send and receive email via text messaging. TeleFlip works with any email account that doesn’t require a secure connection to the Web. That applies to all the major Web-based email providers, including Yahoo Mail, Hotmail and Gmail.

Signing up for TeleFlip took me under five minutes. All I needed to enter was my Gmail email address and password, my cellphone number, and a confirmation number that TeleFlip sent to my cellphone — via text message, of course. TeleFlip then had me build a “whitelist” of contacts, by importing my address book or manually adding email addresses. If I receive an email from someone not on that list, I don’t get it on my cellphone — an annoying quirk. (TeleFlip has plans to let users access all of their emails, beginning around August.)

TeleFlip does what it promises — but it’s neither fast nor pretty. It took from three to 35 minutes for TeleFlip to text me my emails after Gmail received them, averaging about 10 minutes. Because cellphone carriers typically limit text messages to 160 characters, TeleFlip chops each email into snippets, sent in successive text messages. You can decide how many snippets you want to receive. I thought three was enough to get the gist of the messages.

You can also instantly send email. TeleFlip assigns a nickname to each of your contacts — the first six characters of their email address. To send email, text TeleFlip at 33715 and type the recipient’s nickname and the message — for example: “walt.m Thanks for your email. I’ll get back to you soon.” It will appear to the recipient as if it came from your email, not your cellphone.

One turnoff: Each time I received an email via TeleFlip, the company sent a one-time email to the sender telling them about TeleFlip. I found that intrusive. TeleFlip says it will let users disable those emails starting around August.

To search the Web, I tried services from Google (GOOG), Yahoo (YHOO) and 4info. Google can be reached by sending a text message to 466453 (”Google”); for Yahoo, text 92466 (”Yahoo”); for 4info, text 44636 (”4info”).

To find information, it’s useful to know some shortcuts: For a stock quote, text message a ticker symbol. For sports scores, type a team’s name. For local information, type “weather,” “movies,” or the name of a local business, along with a ZIP Code or the name of a city. In my tests, all three services responded accurately to my text messages in under 10 seconds.

Each service has unique features. To find local businesses, I liked Yahoo because it includes cross streets. For instance, when I searched for a certain Indian restaurant, Yahoo gave me its phone number and address, as well as the text, “Near the intersection of Valencia St and 21st St.”

I liked that 4info lets you set up customized alerts to your cellphone — texting you, say, when Target’s stock falls by more than 5% (4info.net/alerts/add/stock) or when a Red Sox game ends (4info.net/alerts/add/sports).

Google, meanwhile, sends you driving directions if you text it this: “directions from (address, city or ZIP Code) to (address, city or ZIP Code).” You can also do rudimentary searches by texting Google: “web” plus the search term.

In response to Web-search queries, Google typically sends back text messages with words from the top search results. So, be extra-precise with your search terms. While parking my car, I couldn’t remember what a blue curb meant. I texted Google, “web blue curb” and got an unhelpful result from a university Web site. Next, I typed, “web parking blue paint curb” and received a message telling me that a blue curb designates parking for the disabled.

With Google Calendar, you also can check and update your calendar using text messaging. To start, visit calendar.google.com. Click “Settings” in the top corner and then click the “Mobile Setup” tab to register your cellphone for notifications. Click the “Calendars” tab. Next, click “Notifications” and follow instructions.

You can receive text-message reminders for events. You can also ask for a daily agenda, or even get reminders on the fly at 48368 (”Gvent”). Texting “day” got me the day’s schedule, texting “next” got me my next event and texting “nday” got me the following day’s schedule.

My favorite part: You can add events to your Google Calendar by texting “Gvent.” To add a dinner date for the following week, I simply wrote, “dinner Tuesday 7 pm.” When I visited Google Calendar online a few minutes later, the event was already listed.

• Send email to Vauhini.Vara@wsj.com. Walter S. Mossberg returns on June 5.

There are tools for dealing with the problem, most commonly, filtering software that attempts to bar sexual, violent and other objectionable material. But these can frustrate kids and parents, by either blocking too many things or not blocking enough.

Avatars help guide users

Some other approaches, such as the parental controls built right into the latest Windows (MSFT) and Macintosh (AAPL) operating systems, offer parents more control by allowing them to specify what Web sites a child can access. But that requires close and constant involvement by the parent as the child seeks access to more Web sites.

This week marks the launch of a parental-control service with a somewhat different approach. It’s called KidZui, and it aims to offer kids a safe subset of the Internet where they can roam freely without triggering parental worry. KidZui, for children ages 3 to 12, hopes to emphasize the positive, rather than the negative.

The service, from a San Diego company of the same name, claims to encompass 500,000 safe sites, photos and videos, ranging from pop culture to science, comics and games to history. You can watch the latest “American Idol” contestant, learn about dinosaurs, delve into history or visit popular kids’ sites, such as Webkinz and Club Penguin.

The sites, photos and videos included in KidZui are approved by a team of about 200 parents and teachers across the country, and are ranked by age, so that a site that might be right for an 11-year-old isn’t served up to a 4-year-old.

While a child can establish a list of friends in KidZui, and can share content with them, there is no instant-messaging or email function.

KidZui isn’t free, and it can’t be accessed via a regular Web browser. Instead, you must download a special KidZui browser, from kidzui.com, that runs on either Windows or Macintosh computers. I tested it on both platforms, and it downloaded quickly and installed smoothly.

The service nominally costs $99.95 a year, or $9.95 a month, but there is a 30-day free trial and an introductory rate of $49.95 a year, or $4.95 a month. It has no ads, other than those already present on Web sites kids visit.

A key selling point of the service is that busy parents can simply set up KidZui and trust that their kids will be safe online. To that end, the program can be optionally configured, so that a child can’t escape from it to use the computer’s standard browser, for example. A parent can set KidZui to launch when the computer starts up, in full-screen mode. In this mode, KidZui automatically disables or hides the common keystrokes, icons, commands and techniques that allow users to switch to, or to start up, other programs.

In addition, when KidZui is running in this locked-down mode, the child can be barred from quitting KidZui without a parent’s password. In my tests over the past week, I found some loopholes in this lockdown system, but the company plugged each leak I turned up. I can’t swear that a clever kid won’t be able to escape from KidZui, but the program blocks most obvious exits.

Inside the software, the company has tried to create a fun, lighthearted world. Each child is represented by a “Zui,” a cartoon-like character that can be customized with hair, clothing and other features. There are lots of sound effects, and kids can rate content with illustrated tags ranging from “best” and “cool” to “boring” or “gross.”

When a child types in a term like “ocean” KidZui offers a list of related terms as well, to guide further exploration. If a child types in a search term or a Web address that has been banned from the KidZui universe, a message appears saying “This page isn’t available on KidZui, but your parents can add it for you.” This applies not only to terms typed into KidZui’s own search bar, but also to terms a child enters at sites like Wikipedia or in the search boxes embedded in other sites. The main pages of Google and Yahoo can’t be summoned.

If a search or Web address is new to KidZui, a different message appears promising that it will be reviewed.

I did find some holes in this system. For instance, I was able to get to The Wall Street Journal’s Web site and do an internal search on “Spitzer,” which turned up a story on the former New York governor’s sex scandal.

Parents can get detailed reports about the KidZui activities of each of their children and can tweak the content they can see by adding specific types of material, such as “athletic violence,” and approving or blocking specific Web sites.

For parents who want to allow limited Web use by their young children without constantly micromanaging their online activities, KidZui may be worth a try, but don’t expect it to be perfect.

Email me at mossberg@wsj.com. Find all my columns and videos online, free, at the new All Things Digital Web site, http://walt.allthingsd.com.