how-to block ads
said by GMAIL FAQ:
About Ads & Related Information
You've reached this page because you chose to read more about ads and related pages delivered by Google. Ads in Gmail are placed in the same way that ads are placed alongside Google search results and, through the Google AdSense program, on content pages across the web.
Related information provides relevant information from sites in Google's extensive index of web pages.
Gmail is a technology-based program. Advertising and related information are shown using a completely automated process. Ads are selected for relevance and served by Google computers using the same contextual advertising technology that powers our AdSense program. This technology enables Google to effectively target dynamically changing content, such as email, or news stories.
No humans will read the content of your email in order to target such advertisements or related information. Because the ads and Related Pages are matched to information that is of interest to you, we hope you'll find them relevant and useful.
Google does not and will never rent, sell or share information that personally identifies you for marketing purposes without your express permission. No email content or other personally identifiable information will be provided to advertisers.
Privacy is an issue we take very seriously. Only ads classified as Family-Safe are distributed through our content network and to your Gmail inbox. For example, Google would block certain ads from running next to an email about catastrophic news.