If you looking to add language translation functionality into your website so that non-English speaking visitors can read your pages in their native language, you have a couple of good options to choose from. Google Translation Widgets are available as a JavaScript based Language drop-down, as a overlay toolbar, as AJAX for in-place translation and as plain HTML.

If you are thinking to add it, wait it may harm you web ranking in  Search engine. I spotted an interesting comment from Google's JohnMu at the Google Webmaster Help forums. John said that in some cases, using Google Translate to auto-translate content for your web site might be seen as "creating auto-generated content, which would be against our Webmaster Guidelines."

"I just want to add a word of warning here -- using automated translation tools to directly create content for your site could be seen as creating auto-generated content, which would be against our Webmaster Guidelines. Instead of just taking the output of a program like Google Translate, I'd strongly recommend at least having it corrected before putting it online. While Googlebot may initially fall for some Spanish keywords in your text, your users are not going to appreciate content that has been automatically translated and published without a review. I love Google Translate, but if you publish the results and get them indexed without having them reviewed, you're not showing a lot of respect to your users... A great way of working together with translators on a text is the Google Translator Toolkit: http://translate.google.com/toolkit?hl=en"

Then i searched their webmaster guidelines. They've written this:

One of the most important steps in improving your site's ranking in Google search results is to ensure that it contains plenty of rich information that includes relevant keywords, used appropriately, that indicate the subject matter of your content.

However, some webmasters attempt to improve their page's ranking and attract visitors by creating pages with many words but little or no authentic content. Google will take action against domains that try to rank more highly by just showing scraped or other auto-generated pages that don't add any value to users. Examples include:

• Thin affiliate sites: These sites collect pay-per-click (PPC) revenue by sending visitors to the sites of affiliate programs, while providing little or no value-added content or service to the user. These sites usually have no original content and may be cookie-cutter sites or templates with no unique content.
• Doorway pages: Pages created just for search engines
• Auto-generated content: Content generated programatically. Often this will consist of random paragraphs of text that make no sense to the reader but that may contain search keywords.
• Scraped content: Some webmasters make use of content taken from other, more reputable sites on the assumption that increasing the volume of web pages with random, irrelevant content is a good long-term strategy. Purely scraped content, even from high-quality sources, may not provide any added value to your users without additional useful services or content provided by your site. It's worthwhile to take the time to create original content that sets your site apart. This will keep your visitors coming back and will provide useful search results.

There is no problem in being an affiliate as long as you create some added value for your users and produce valuable content that gives a user a reason to visit your site. For example, you could create product reviews, ratings, and product comparisons.

If your site has been removed from our search results, review our webmaster guidelines for more information. Once you've made your changes and are confident that your site no longer violates our guidelines, submit your site for reconsideration.

So, before using google translate for your website think about automatic generated content, which may be harmful for your website.

Is it possible to translate all content in tradition way if you have huge database?