Be smart and think ahead when you post content online. If you post something questionable, you can bet that someday, someone will find it. Google and other search engines are only getting better at digging up and delivering accurate search results.
Adopt the attitude that if you post something to the Internet, it's there forever. Even if you delete an original post deriding your boss, there's a very good chance that a copy of that message has been duplicated and transferred to other parts of the Web.
For example, even though a Web site is no longer functional, you can still view cached copies that Google stories years after the site is shuttered. The same goes for your blog and even e-mail messages.
Not everyone is happy about the Web's long memory. Some experts are pushing for data to have a so-called expiration date that obliterates data once it has reached a certain age. However, expiration dates or related technologies are probably years away, meaning your own vigilance is your best protection.