When you receive a mail/message which contains a link to a well known site where you are asked to enter your login and password.You login and after a few hours or days you realize that the account into which you logged in has been hacked. If this has happened with you then you had been a victim of phishing. And this is most common on yahoo.
Definition on answers.comHere are a few things that you can do to prevent phishing.
--> Pay special attention to the location bar of your browser. For eg if you are being asked to login with your yahoo account. Even if the copy and page design look like yahoo, double check the URL. If it isn't yahoo.com or www.yahoo.com(or the simmillar onces like yahoo.co.in, yahoo.co.uk etc), it's not Yahoo!.
--> If you are not sure, unable to decide the genuineness of the link then
login with a wrong login name or password. In most cases false sites take you to the correct link on doing so.
--> And in case you've logged into such site and then realize that this was a fake site(may be by the webpage you get redirected to after logging in or by intuition or sixth sense :D) then
change the password of your account as soon as possible.
The following link has some
pics of sites that pretending to be Flickr. But they are not flickr. They are phishing!!
Instructions by Flickr on phishing