Ok, so i understand paid links are a problem and can be penalized heavily by google, but how does google know when a link is paid or not? If i link from the bottom of every page in my current werbsite, to promote my new and unrelated site, will i get penalized? Just need to try and clear up how they google works out whats paid on not paid, so any answers are appreciated.
Footer links aren't natural. Site wide links aren't natural. When someone naturally links to your site, they usually do it inside of an article or post and don't do it more than once or twice. If your sites are with the same host, you should forget about trying to pass link juice as google is going to assume they share common ownership. Linking to a site with unrelated content isn't going to help much anyway. Concentrate on building a site that is so good people will naturally want to link to it.
does google detect source code? if Google detect source code, im sure it will be easy to detect paid links and paid reviews. Because paid links and paid reviews are using some custom tracking script.