Can I Hide/Password My Pages or Whole Blog?
Yes, but do you need to?
Almost all systems have ways to hide individual posts or a whole blog, so that they can only be accessed with a password. You can run a private blog where only certain people can post to the blog, and/or only certain people can read the blog.
Many people want to hide their blog until it's "ready". This isn't necessary. It's better to start working on your blog, and make it visible so that Google picks it up sooner. Unless you tell people about it, no one's going to come to your blog straight away anyway.
In WordPress, you can easily install the Absolute Privacy plugin, to hide your entire site, or you can just add passwords to individual posts/pages.