Why it matters
Most "our website doesn't work" complaints are IA problems wearing design clothes: the right content exists but nobody can find it, or pages are organised around your org chart instead of your customers' questions. Bad IA also confuses the engines that decide what your site is about.
How it works
Good IA starts from tasks and questions, not departments: what did the visitor come to do, and what's the shortest path to it? Content gets grouped by those intents, named in the visitor's language, and cross-linked where journeys flow.
What to do about it
List the top ten things visitors come to do, then walk each path on your current site as a stranger would. Every hesitation you feel is an IA fix, and the fixes usually cost far less than a redesign.
