15 years old
While previously the web had been all about finding information, things had started to change by the time it reached the wise old age of 15.
Change number one was that more people started to shop online frequently. Web-based retailer Amazon posted its first profitable year with international sales up 33 per cent on the previous year. Meanwhile eBay had over 135 million registered users, up 43 per cent on 2003. Between them, the two companies had sold or bought almost $10billion worth of merchandise.
SELLING UP: 2004 was Amazon's first profitable year, with sales approaching £7 billion
In the UK, specialist e-retailers were joined by the traditional outlets such as Argus and Screwfix, who were soon to be up there with Amazon at the top of the league table for online shopping. With low-cost airlines, holiday companies and the major supermarkets also providing an online ordering service, around 33 per cent of Britons were now shopping online. Each spent an average of over £500 per year. Goods worth £3.3billion were shifted in the 10 week run-up Christmas. Mainstream online shopping had come of age.
Change number two was the way in which social interaction happened online. The likes of MySpace and Facebook were still small fry, but their predecessors were starting to get a foothold. As blogging really took off, web users got into the habit of providing web content rather than just consuming it for the first time.
Instant messaging was also in a period of massive growth. Strictly speaking, IM isn't a web application (because behind the scenes it doesn't use HTTP) but most users don't care about the nuts and bolts, and it's an important stepping-stone to social networking.
Chatrooms were also taking off, and in one way or another vast numbers of people were interacting with each other online without the delay inherent in email exchanges.
20 years old
Twenty years on, all of the technologies and trends we've seen emerge in two decades are still going strong. The mainstay of the web is still hyperlinked pages of information, even though many of those links are now graphical rather than blue text and active content is the rule rather than the exception.
Search engines continue to flourish alongside newer web presences such as online shopping sites. Does this mean the web is now mature and the days of change are long gone? Not a bit of it.
At our last milestone, many of the changes to the web were inspired by commercial and social pressures rather than technology. But in the last five years advances in technology are, once again, making their impact felt.
Five years ago, only seven per cent of the UK's internet users had a broadband connection, far behind much of the rest of the developed world. By 2007, half of all adults in the UK had fast internet access at home and, as of today, 95.1 per cent of all the UK's connections to the internet are via broadband.
Connection speeds have also escalated. Today the average speed a broadband user in the UK can expect is 4.3Mbps. Virgin's cable broadband offers up to 50Mbps. Worldwide, even higher speeds are available – 100Mbps is considered normal in Japan – so it's no surprise that the web of 2009 has taken advantage of all this extra bandwidth.
First and foremost this means more multimedia content. YouTube would be barely usable over a dial-up connection. Today, millions of people have taken heed of the site's invitation to 'Broadcast Yourself', with 15 hours of video being uploaded to the site every minute. In the US alone, over 100 million viewers watch over six billion movies per month.
The BBC iPlayer is another beneficiary of high-speed internet connections. Launched in December 2007, it's still the new kid on the block but already the iPlayer is providing over half a million people a day with the opportunity to watch programmes they've missed or view again those they enjoyed.
WATCH THIS SPACE: The BBC iPlayer, which attracts millions of visitors, is only viable because of the massive take-up of broadband internet services over the last couple of years
The other big success story is the iTunes Store, the music download site provided by Apple in the wake of the hugely popular iPod. To date, downloads account for less than 10 per cent of music sales, but with CD sales falling, it's clear where the future lies.
But the popularity of broadband doesn't mean that the web is now solely about multimedia. As Google Earth has shown, the public still have an appetite for information. Using a smart plug-in, the user's PC can interact with a database of satellite imagery on Google's computers. As a result, 2.5 million people a month in the UK alone are experiencing what was formerly the sole domain of the military.
Technology has also come to the fore in the case of the mobile internet. No longer is browsing the web only something to be done sitting at a desk. With the combination of Wi-Fi hotspots, web-enabled mobile phones and the new MID (Mobile Internet Device) platform, we can go online anywhere. This ability is also key in changing how we use the web.
With the exception of keeping up to date with the news, a recent survey has shown that social networking is the major reason for accessing the web while out and about. If you're used to being able to text friends anywhere, it doesn't make sense that you can only contact them via social-networking sites while sitting at your desk. The mobile internet has catapulted Facebook and MySpace into the major league.
Meanwhile, in a bizarre example of how the web at 20 is affecting lives, a British woman is divorcing her husband because his alter ego in the online community Second Life had an affair with a virtual woman in a virtual world.
25 years old
With web technology showing no signs of running out of steam, it's inevitable that the web of 25 years will be markedly different from the web of today. What we don't know yet is exactly how it will evolve. We spoke to Rohit Agarwal, Director of Marketing and Innovation for AOL Europe, to get an idea of how the web could evolve even further over the next five years.
Agarwal's vision of the future revolved round three key themes – web access versus web experience, voice-enabled web and the realisation of cloud computing.
"With the world permanently and ubiquitously online, the question will be about the user experience," says Agarwal. "Access to the web and to the information you want will be available anywhere and at any time from a whole myriad of devices.
MOBILE INTERNET: More and more traffic on the web is destined for devices other than the PC
"The iPhone may be credited as the device that first made the mobile internet a truly enjoyable user experience through its large touchscreen display, and similar handsets are being produced. But this is only one side of the move away from the desktop as the main point of contact with the web. The other side of the development will see television and the web fully converge, giving a more complete and interactive experience."
"Voice-enabled web will make it possible to control your computer through voice commands," says Agarwal. "Microsoft and Nuance serve as incumbents to this technology, and other companies have the opportunity to develop it.
"Through the realisation of cloud computing we will be able to synchronise our online life and always have access to our personal media assets, no matter where we are. We will be able to edit, create and share movies, documents and personal media within this cloud through online apps that no longer require local software installation."
Agarwal stressed that many of these technologies are already with us. "The key", he said, "is that they will continue to converge, becoming an interconnected personal experience and adding value to each part of your everyday life."