Question

a(n) ___ is a web page or small website that contains a series of chronological posts and comments. blog aggregator wiki forum

Explanation:

A blog is a web page or small website that contains a series of chronological posts and comments. An aggregator collects content from various sources. A wiki is a collaborative website where users can edit content. A forum is a discussion site where users can post messages. The description in the question matches the definition of a blog.

Answer:

blog