Planet13 - 8:16 pm on Jan 24, 2012 (gmt 0)

I was wondering if anyone had experienced their homepage no longer ranking for a term and a subpage of the site ranking instead, usually lower. Why does this happen to some sites and not others?

first, check for technical errors. Check, then double check, then triple check.

for example, I accidentally noindexed my home page for over a month. Doh! It took someone else to point this out to me.

check that you don't have a canonical link tag on your home page pointing toward a different page. Also check that you don't have both the www. version as well as the non www version returning 200 responses. One should be 301 redirected to the other.

with the symptoms you describe, I think it is one of the above situations. Otherwise, it might be bad coding, such as two head tags, or something like that.