Just use an Internet-based service so that you can chat from a Web page without having to install any software, which might be blocked by a firewall. I tested two such services: Meebo at www.meebo.com and KoolIM at www.koolim.com. Both are free.

These services let you simultaneously log in to multiple IM accounts — and communicate with people with various services. If you have a friend who uses Yahoo Messenger, for example, and another who likes MSN Messenger, you can chat with either.

Another plus: Meebo and KoolIM are far less vulnerable to viruses than downloadable applications. They’re also more efficient, saving users the hassle of installing multiple programs on a computer. This is especially handy for people with old computers that slow down when running several applications.

Meebo has a well-designed, sleek interface that makes it appealing to even the least tech savvy. From its home page, you simply sign in for different IM services—MSN Messenger, Yahoo Messenger, GTalk (or Jabber) and AIM (or ICQ). Your buddy list will be combined automatically. You don’t have to register, but if you do, you get perks such as a single sign-on for all of your accounts, and the ability to share files, save chat logs and store conversations.

I tried Meebo on my work Windows PC and my iBook at home, and it worked well on both. To start chatting, you just log in to any of the IM services by entering the screen name and password you already have with a service, or by picking a new name, password and services. Your buddy list will appear in a window on the right side of the page, with each name marked by an icon denoting the service the person uses. Once in your buddy list, you can add or delete a contact, message or join a group chat.

The service also offers MeeboMe, a way to chat from your own Web site. Bloggers can use this to start a conversation with site visitors who log in to their Meebo account. It also shows how many users are on the site at any time.

But Meebo, like most such Web services, lacks the ability for audio and video chats — basic features on installed IM software. If you’re used to plugging in a Webcam and headgear to chat with friends, these services might not be for you. Meebo also doesn’t have the standard send button that’s on installed IM software. Instead, you press a key on your keyboard.

Sharing files using Meebo is tricky, too. Only Meebo account holders can send files; although anyone can receive them. When I sent a PDF file to my friend on her installed MSN Messenger, she received a message and a link that rerouted her to Meebo’s home page with no further guidance. When I sent her the same file after she logged in to her MSN using Meebo, she could open the file.

KoolIM also connects users to multiple IM accounts from one Web page. It gives you the option to create an online account, so you don’t need separate log-ins for each IM service you’ll encounter.

You can select an embedded or a pop-up version of the service. The embedded version shows your buddy list and messages as windows tied to a Web page, while the pop-up version lets you move the windows around the screen. You can choose to display all of your buddies or only the ones online. In your buddy-list window you can add and delete names and log in to or out of a service.

I didn’t like having text ads appear at the bottom of the IM window in KoolIM, or the fact that, unlike Meebo, there isn’t a time stamp on messages to tell you when they arrived. It also doesn’t allow you to send files, as Meebo does. And it doesn’t let you save conversations or chat logs. KoolIM’s lack of some of these basic features might make it less appealing to consumers, especially those who ponder swapping it with their desktop software.

I preferred Meebo, but both services are good alternatives to installed IM, if you’re willing to do without audio and video features.

Walt Mossberg is on vacation. Find all my columns and videos online free at the new All Things Digital Web site, http://walt.allthingsd.com.

• Email me at Sarmad.Ali@wsj.com.

The result is a polished, fairly powerful email program that I prefer to Google’s much-hyped Gmail, which is undergoing an even longer gestation. It has been in beta status since April 2004.

I’ve been testing the new Yahoo Mail on both Windows and Macintosh computers. It has some downsides, but it beats Gmail, in my view, both in terms of features and in terms of its ability to act like a standard computer program rather than a Web page, something for which Gmail often gets more credit.

A closer competitor to Yahoo Mail is actually Microsoft’s Hotmail, now called Windows Live Hotmail. But Yahoo tops Hotmail, too, in my opinion.

The new Yahoo Mail, which works in Internet Explorer and Firefox on Windows, and in Firefox on the Macintosh, is now more than just an email program. Like Gmail, but unlike Hotmail, it has a built-in instant-messaging module. You can choose to communicate with any of your contacts via a real-time chat, right from within Yahoo Mail, as long as that contact is online and has an IM account on either the Yahoo or Microsoft instant-messaging networks. You don’t need to be running your IM program.

Unlike either of its competitors, however, the new Yahoo Mail also allows you to exchange text messages with people on cellphones, although the message exchange must be initiated from Yahoo Mail.

Yahoo Mail offers unlimited storage of emails and attachments free of charge, and a very fast and good search capability — like Gmail’s — so you can keep years of messages on hand and retrieve them quickly. Gmail offers 2.9 gigabytes of storage free. It sells extra storage for prices ranging from $20 a year for six gigabytes to $500 a year for 250 gigabytes. Hotmail is in the process of boosting its storage to five gigabytes, free, and 10 gigabytes for $20 a year.

With Yahoo Mail, you can send attachments of up to 10 megabytes per message and 20 megabytes if you opt for a $20-a-year plan that also eliminates the annoying banner ads that litter the free version. Gmail offers attachments of up to 20 megabytes free. Hotmail allows 10 megabyte attachments and 20 megabytes under its $20-a-year plan, which also banishes ads. Gmail has no banner ads, just text ads that run alongside the emails and can’t be eliminated.

This new Yahoo Mail is gradually being rolled out in coming weeks. The company still plans to retain the older version of Yahoo Mail, now called Classic, for people who prefer it, or for those using browsers that are incompatible with the new version, such as Apple’s Safari.

The new Yahoo Mail allows you to do things that once were impossible in a Web-based email program. For instance, you can drag messages to new folders, or select a group of messages in the same way you would with a standard email program, to delete them or mark them as read or unread. Unlike in Gmail, when you right-click on a message you get a list of options that pertain to the mail program — like “Reply to Sender” — instead of options that pertain to the use of the browser — like “Add to Favorites.”

Also, Yahoo Mail features a very nice tabbed interface that Gmail and Hotmail lack. With this interface, which is separate from the browser’s own tabs, you could have your inbox in one tab, an instant-message or text-message conversation going on in another and a new email you are composing occupying yet another. You can move among these tabs without losing the content in any of them.

And like Hotmail but not Gmail, Yahoo Mail offers a preview pane, like Microsoft’s Outlook, so you can see the contents of an email without opening it. Gmail offers just a “snippet” of the message content. Unlike Gmail, which forces you to view your emails as bunched-up “conversations,” Yahoo Mail — like Hotmail — displays them as a standard email program does, sorting them by date, sender, subject or size.

So what are the downsides of Yahoo Mail?

Well, the biggest is probably that unless you pay for the $20-a-year premium plan, you can’t view your Yahoo mail account in a standard email program such as Outlook or Apple Mail. Gmail allows this free of charge. Hotmail allows it free in Outlook and in Windows Mail, though it will soon announce the capability for other email programs for premium members and, eventually, for free members as well.

Also, I found Yahoo Mail could sometimes be slow. When I created a new folder and tried to drag 200 emails into it, I was warned that I couldn’t do that because the new folder was “still being created.”

But overall, Yahoo did a really good job making its online mail program versatile, powerful and accessible.

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.