If a website advertise something for a price are they obliged to sell it for that price?

In general, advertisements are considered invitations to treat rather than legally binding offers. This means that a seller is not legally obliged to sell an item at the advertised price if it was a mistake or misrepresentation. However, businesses may have a moral or reputational obligation to honor advertised prices to maintain customer trust. Local laws may also vary, so it's important to consider specific regulations that could apply.