Sidebar at bottom (Mines is a different issue from all the old posted question )

Mines is a different issue from all the old posted question

not a chance – same cause: code slashing.

a:
I only see the problem in single posts, not on the front page.

b:
you seem to have messed with the ‘entry-meta’ section in single.php, removed the opening div but left the closing div.

replace it with an original section from a fresh download of the ‘tiger’ theme.
or replace the full single.php;
then re-do the changes.

AND how they KNEW what was wrong?

for instance, look at the html in the browser, using the ‘view source’ of Firefox – faulty codes are shown in red.
also, try to use Firefox’ web developer add-on or Firebug