For successful search engine optimization (SEO) it is necessary to have text-based content rather than images and flash, Google has said.

Kent Sugarman from AdSense Publisher Support said while the search engine giant is constantly innovating, its spiders currently base their rankings on the type of text on a site.

This is because they are unable to understand the content of flash, images and video streaming, he continued.

Mr Sugarman said people using the AdSense service may suffer because they are not using enough text.

"Although images, flash, and streaming video can help spice up a site, relying heavily on these sorts of elements will make it difficult for us to get a good read on what your site is about," he added.

Tips for improving SEO and AdSense targeting include using text as well as images and imagining the website without images to understand what Google spiders can see.

Last month Microsoft claimed to be able to better understand users’ desires than its rival Google.

Academics and researchers wrote in BrowseRank: Letting Web Users Vote for Page Importance that with MSN search, sites were judged by how much time people visited and spent on particular websites.