Can I participate in a Yahoo group exclusively on the Web?

No question, there's nothing you can do with Yahoo Groups coming to your mailbox that you can't also do with the quite slick Web-based interface. In fact, I'll show you how you can post a message to a Yahoo Group, to My LinkedIn Power Forum, so you can see how easy it is.

When you're logged in to your specific group, you'll see the following menu on the left of every page:

You can see the needed link: Post. Click on that and you'll be able to compose a message to your heart's desire:

As with any group or online publishing venue, I strongly suggest that you make sure your title is informative, interesting, and helps guide people on the actual topic of your posting.

Notice also that when you're reading a specific message, you can respond that specific message by clicking on Reply:

Lots of choices, but, as you can see, it's pretty darn easy to figure out how to interact and join in the conversation on a Yahoo Groups discussion group. Hope that's helpful!