Firms could be more likely to generate sales by placing online advertisements across various websites.

According to research conducted by the Atlas Institute, users are twice as likely to make a purchase or opt in to a service if they have been exposed to the same set of adverts on different portals.

The findings also indicated that the effects of overlapping adverts needs more recognition as by traditional measures marketing is reported to focus too much on the last ad viewed.

Study author Jed Fowler said: "The study validates the fact that most marketers need to plan beyond the last ad seen."

"It's critical that marketers review all consumer touch-points to determine credit for conversions," he added.

In related news, figures from Hitwise have revealed that an increasing number of click-through traffic to retail websites comes from search engine queries.