The customisation of cyberspace continues apace, with Yahoo's launch today of My Web, a "personalised search engine".

The online advertising company hopes that the service, which will allow users to store and share virtual "photocopies" of web pages and search results, will draw in audiences to feed Yahoo’s booming advertising business

"We think about these things in terms of users, advertisers and publishers," Salim Mitha, the director of Yahoo Search in the UK, told Times Online.

"With My Web, we are primarily aiming to increase users’ control over the web. With that comes increased user engagement, which benefits publishers and feeds into the advertising side of our business."

My Web, which is being launched as a beta, or test, version, allows users to create online folders to store exact copies of online documents such as e-tail receipts or travel itineraries. It will also allow users to annotate stored web pages and to search for their notes through a desktop toolbar.

The folders are accessible from any online computer - in the same way as web-based e-mail accounts.

"This all sounds incredibly basic, and it is," said Mr Mitha. "But the fact is, nobody has put together anything like this before."

My Web users will also be able to share folders with the outside world, offering people the opportunity to access a folder's contents via RSS feeds, which allow users to cherry pick relevant information sources and have content directed to them.

The system also joins up with 360º - Yahoo’s social blogging site -and is likely to compete with services such as MSN Spaces, Microsoft's blogging tool. The emphasis on "personalised search" also recalls the recent marketing pitch for MSN Search, Microsoft's own search engine.

The new offering from Yahoo is the latest in a string of products designed to manage information drawn from the internet. Importantly, it could allow Yahoo to differentiate itself from its arch-rival Google.

Yahoo, which started life in the early 1990s as "Jerry's guide to the world wide web", a single page run by two university students, and now claims to be the most popular website in the world, already competes with Google in the search engine stakes. Likewise, each company offers a desktop search service that allows users to find information on the hard-disks of their computers.

But it is through advertising that both companies make the vast majority of their money. The competition increased this week when Google moved into display advertising for the first time, joining Yahoo in offering animated ads, which are used to build up brand awareness.

Google said the move represented an acknowledgement of advertisers' comments, providing clients with more control over where their adverts appear.

Meanwhile, paid-search advertising, where clients pay to be placed at the top of a list of search results when certain keywords are entered, remains the fastest growing sector online. Jupiter Research recently estimated that it will grow from $2.6 billion in 2004 to $5.5 billion in 2009.

Yahoo will undoubtedly hope that My Web will draw users to it's search engine and boost paid-search revenues. However, executives at the two companies have played down their rivalry.

"We think the market is big enough for the both of us," Kate Burns, managing director of Google's sales and operations in the UK, told Times Online.

"After all, online advertising accounts for only around 4 per cent of the overall advertising market. The online market has a lot of work to do to catch up. We can't afford to get distracted."

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