It can flow directly from your information design process or help inform it where you start doesn't actually matter but be prepared to do a little back and forth.
Web design is very much a reiterative process.
You will need to craft a blueprint that illustrates where users can go and what they can do at any location in the site. Site maps come in several flavors, as a visual diagram of the maintain content sections at the site or in text format as a table of contents. You will need to start thinking about page layouts and templates and how the various graphic elements will work together, not compete. The content or graphics that appear on your Web page come launch day will certainly change either incrementally or dramatically over time. From the day your site goes public, you will probably be adding new sections, deleting sections that don't work well, and modifying others.