If you thought pop-ups couldn't get any more annoying...

Pop-up ads, already the bane of millions of web surfers, are set to become even more intrusive.

Pop-up and pop-under ads open a new window when people visit many popular websites, often littering the computer desktop with multiple browser screens. Advertisers hope people will visit the promoted web page by clicking anywhere on the window, although many simply close it by selecting the 'X' box in the top-right corner.

But a relatively new feature may make it harder for people to avoid these windows. Using a technique called the 'kick through', advertisers can direct a person to another website if they simply move their cursor across the pop-up ad - no clicking is necessary.

Discount travel retailer Orbitz, for example, is delivering millions of holiday-themed kick-through ads on The New York Times website, ESPN.com and CondeNast sites in addition to others. The ads feature various animated games, and recipients who simply 'mouse' over them are shuttled to Orbitz's home page.

Many people who have encountered the ads say they overstep the boundaries of an already intrusive and loathed form of web advertising.

Stefanie Olsen writes for News.com