I have two blogs. I was wondering if anyone else posts illegal contents in my blogs, will it legally affect me?
IANAL, but have a disclaimer on your blog and you should be OK. That being said, you should remove content if you think you might get sued over it- better safe than sorry.
Sure you can be sued (and disclaimers won't protect you at all from a lawsuit). Whether such a lawsuit would be successful depends on what the comments actually say and what country you live in and your site is hosted in (UK law, for example, makes it much easier for people to go after someone for libel, than the law in the US). Here's a real example, from an article written in the Wall Street Journal in 2005: "Blogger Faces Lawsuit Over Comments Posted by Readers". And read the blogger's account of it here: "Fighting for Bloggers' Rights" That particular case was thrown out in 2006, but note that the blogger in question still had to go to court and file a motion to Dismiss - and the case was dismissed over jurisdictional issues, rather than because the case itself was bogus. But the reality is that, unless you are writing about something contentious like politics or scams or football, it's unlikely anyone will comment in a libelous way. And more practically, it's usually the commenter who gets sued, rather than the blogger.
In theory you are protected by the Common Carrier rule, however even if you prevail in litigation you still lose considering the cost of defense. Best policy is to police the content of your blog to the best of your ability.