There is a option almost in every web browser to save passwords.Can any site know these passwords from browser?I these passwords are saved in encrypted format?
Typically browsers (assuming they are not vulnerable - which they might be) do not provide a method for websites to get your passwords, however, if you have not set a master password or opted for an encrypted profile, it will be easy to for other programs to snatch them. So it is a good practice to have a master password set.
Fimally, bear in mind that most of the modern browsers (read Chrome and Firefox) can, and sometimes subliminally sync your profile, which MAY include your passwords. That means that saved passwords are not only stored on your machine but also on the sync servers.
Just so that you are aware of some of the risks.