One of the cleverest features in Apple’s iChat is the screen-sharing option that lets you view the desktop of another person’s Mac on your own computer. You can even take control of the other Mac in order to fix a problem or show them how to do something.

It’s really handy, but iChat does have certain limitations. You can only share screens between two people at a time, and it only works with Macs. The online screen-sharing service works with both Macs and PCs, and allows you to share your screen with up to 250 people at a time. This is very useful for setting up online meetings and presentations where you can share information with your colleagues.

The only minor drawback is that requires Adobe Flash – so you can’t join in a screen-sharing session when you’re lounging at home with your iPad or iPhone.

1. On the button  To activate a screen-sharing session or to join a session that has already been started by someone else, just enter (with no .com) as the address in your web browser. That will take you straight to the website, where you’ll see two big buttons labelled Share and Join.

2. Click to share  You can use the service for free, although there is a subscription-based pro version available. Click the Share button to start a session and your web browser will download the software you need to control the screen-sharing session. Then just follow the prompts to install the software.

3. Entry code  Once the software has been installed, you’ll see an orange toolbar appear at the top of the screen. Notice the numerical code displayed here – this is the access code that other people will need in order to join your screen-sharing session. Make a note of it, as you’ll need it later on in the session.

4. Joining in  You’ll need to send the access code to everyone who wants to join the session – either by phone, email or instant messaging. Here’s Internet Explorer running on a PC being used by one of our colleagues. All they have to do is go to the website, enter the access code, and click the Join button.