Do ids in heading tags affect search engines?

Matt's answer:

CUTTS: All right, we’ve got a question from Spain, specifically Madrid. Dictina asks, “Does using a class or an ID in a header tag instead of plain headers interfere with the way search engines see and understand the headings?” And I believe the answer is no because you still have, for example, h1, you just have h1 ID equals whatever. So, I don’t think that interferes in any way. We’re pretty good about saying here’s a hyperlink or an image tag and here are extra attributes, width or height and, you know, we can parse those and sometimes we’ll use them. For example, an image search, you can now search for specific image width and height images. But we are very good about noisy documents, documents with extra IDs and all sorts of DIVs, tables that aren’t closed, those sorts of things. We do pretty well about disregarding those. So I would do clean great syntax, make it easier for yourself when you develop or upgrade your site in the future, and Google will do a good job of ignoring the elements like on DIVs and stuff like that where, you know, you give it a class or an ID name and that’s not strictly necessary. But it’s often a good form to do. So don’t worry about it as far as search engines go.

by Matt Cutts - Google's Head of Search Quality Team

Original video: