There is no one definitive answer to whether or not blog sites are reliable. That said, many people seem to think that they are, and there are a number of reasons for this.
First of all, blog sites are often maintained by individuals who are passionate about what they write about, and who are likely to take the time to ensure that the information on the site is up-to-date and accurate. Furthermore, blog sites typically have a large following, which means that if any errors are made in their content, they will likely be noticed and corrected quickly.
Overall, then, it seems that blog sites are generally regarded as being somewhat reliable. However, as with any type of online information source, it is always worth checking the information before relying on it completely.