There are several important ethical issues to consider with regard to advertising, including:
Packaging goods in order to make them attractive, and showing the customer all the positive aspects of goods, are normal and acceptable business practices. In the same way, spreading information regarding prices, job openings, and the availability of goods and services, are all part of legitimate advertising.
However, Judaism places the full onus of disclosing defects and other shortcomings in the product or service on the seller, even in the absence of any written guarantee. Advertising which hides or glosses over hidden defects, or which promotes the supply of goods and services which are not actually available, would be prohibited.
Furthermore, one is not allowed to advertise goods as having qualities which they do not possess, to make false statements regarding the comparative efficacy of the article sold, or even to use packaging or wrapping that creates false impressions. The advertising of sale prices that are not actually lower than the usual price, or holding 'closing down' sales when no business is being closed down, also constitutes deceptive advertising.
The advertising of luxury goods as necessities falls under the prohibition of giving bad advice, as does putting pressure on customers to buy things that are quite unnecessary for them by seeking to convince them that they are necessary.
The sale of an item on the basis of a false description is referred to as "geneivat da'at" – fooling a prospective purchaser. Such an act would cause that sale to be null and void – a "mekach ta'ut". The item would revert to the original vendor and any payment would revert to the purchaser.