In my primary ledger's COA,The Comany segments have changed to 10,20,and 30 respectively instead of 01,02 and 03 by itself.
That's why when I tried to create a"Row Set" and try to define the rows 'by clicking the account'it tells me that 'Unknown structure ID 50328 for flexfield code GLLE with application ID 101".How can I reverse this thing back to the original state?
P.S I created all the Company,Accounts,Departments as the Tutorial you have thought us.
Also how do I check for ERRORs in the Metalink(by the error ID)?

It cannot change by itself.
The sequence numbers for the segments within your chart of account structure should be 01, 02, and 03 (instead of 10,20,30). I have mentioned that in the videos.
Unfreeze the structure. Change the sequence and re-freeze the structure.
Then click on the Compile button. This should resolve your error as well.

Mr Hasan
I still got an Error message saying' This flexfield has an invalid value set' whenever I try to define a Row Set,when I click the low Account Assignment box.
I am thinking of creating Another COA either by Copying or manual.But How do I import all the data that I have from the Old COA to the New COA?
I really thank you for all the thing that you are doing .

Have you compiled your flexfield? This should have fixed the problem.
Also try running the program:
"Program - Generate Ledger Flexfield"
See if this resolves the issue.
By copying data do you mean copying values? If yes, then try using the same value sets with the new structure. That way you will not have to reenter all values again in new values sets.