I'll be honest---internet searching has made me lazy with capital letters, often times the case of the letter is ignored.
I'm searching the 1860 census at Ancestry.com nationwide for a William and Matilda Rhodus for an upcoming Casefile Clues article. For reasons that aren't really germane to this post, I searched for William Rhodes as shown below with a keyword of "matilda." This would catch households that had a William Rhodes and a Matilda. I had the exact box checked as shown in this post.
The search came up empty, although I knew there was at least one household in Breckinridge County, Kentucky with a William Rhodus and a Matilda in it as I had already found it.
Yet there were "no results."
When I changed the keyword to "Matilda"I still got no result.
Putting Matilda Rhodus in the keyword box worked with exact checked.
Moral of the story--on the keyword uncheck exact.
We may have additional posts on this topic.