This is addressed by giving the blog it’s own URL and linking to it off the main website. I’m assuming that this is a business site, and the blog will have business purpose. Keep in mind that the communication strategy for a website and for a blog are very, very different. The most important thing that you need to do before you start is to clearly define the purpose of the blog (why do you want the blog, what the topic will be), what the publishing schedule will be, and what the quidelines are for comments. Once you define scope and schedule, you need to stick to them. If you fail to plan up front, you will have chaos and the blog will fail.