Is it true that websites know our activity in their websites?

They do get some information automatically. They need your Internet Protocol (IP) address so they can send the web pages to your computer. The IP can be used to get an approximate location for you, but it is not always a permanent, personal identifier. In addition, web sites often store small bits of data on your system known as cookies. These are normally used to keep you logged into web sites, but can, in some cases track you as you browse a site. Unless you choose to give them your name, address, etc, they don't have it. What they can tell is person with id number X in their system browsed the web site and went to these pages.

Some information is usually kept by the website. What information depends entirely on the site. Some probably keep a lot, some don't keep any. Keep in mind that sites can only keep information that you give to them. So, if you go to the site one day and fill out an application with your name and address, they can put that together with whatever you do next time you show up. There are only three ways that they can tie together info about you: a login, if there is one, your IP address, and cookies. A cookie is essentially an ID card that the site sends to you when you first visit, so that it will remember that you're the same person next time you visit. If you wipe out cookies and don't use a login, then it's going to be pretty difficult for them to tie you to what you've done.

Yes everytime someone hit's a website your IP address is recorded in an access log file.

only yahoo spies ... if you are Russian and yo don't love Putin be sure Yahoo will help him to kill ya

i hope not.

Yes, and they also know what website you were on before you clicked on to theirs.