Terms and conditions are often ambiguous, complex and difficult to understand — which may be the reason why many people agree to them without even reading them.

Nearly a third (27 percent) of those people who responded so far to PC Advisor's latest poll admitted they never read terms and conditions before signing up to them. Forty-two percent only read them 'sometimes'.

"It is absolutely imperative that people read them carefully," said Michael Clinch, partner and head of litigation at IT law firm Picton & Howell. "Once you sign up to them you are legally bound."

But often terms and conditions span several pages, which can put the customer off reading them and in some cases even understanding them.

"The problem arises where companies create complex terms for simple transactions, these are not considered commercially relevant and I would advise that people buy somewhere else," said Clinch.

General principles of contract law apply to what can be contained in terms and conditions, the rule is that terms must not be unreasonable. But this is a matter for the courts to decide.

What customers should look out for are exclusion clauses.

"Many computer manufacturers' terms contain exclusion clauses, which limit or completely exclude their liability if something goes wrong with the product," said Clinch. "It is vital that customers read these carefully as this may be the difference between them receiving compensation or receiving nothing."

Terms and conditions must be negotiated and agreed before a transaction occurs, otherwise they are not legal. Once a contract has been signed terms and conditions cannot be changed and both partied will be liable for them.