Need help recovering from 'experiment' in firefox

[Paul E Condon <pecondon@mesanetworks.net>]

I was trying different preference settings in firefox per the long
rookie's query thread. I managed to get my firefox into a condition
where the specified start page in preferences is 'about:blank' but the
actual start page is 'New Tab'. I can change the text in the 'Home
Page:' text box but changing it has no effect on actual start page,
which remains 'New Tab'. And I cannot open the 'about:blank' page
manually. I have all my bookmarkes sites and can use firefox to access
the sites I want, but ---

I know I have used 'about:blank' in the past when I had other problems
with firefox and I was told to go to 'about:blank' and tweek something
to get things working again. Now I need suggestions about what to
change, or remove, in ~/.mozilla to bring back 'about:blank', because
I want it ready and waiting for those rare occasions. 

Of course, I would also like to avoid introducing new damage into my
set-up.

TIA

-- 
Paul E Condon           
pecondon@mesanetworks.net