InnoDB engine is not loading after tuning parameters

Question

After installing MySQL-5.1.73, I placed default my-huge.cnf into /etc/my.cnf and started the mysql service. It was running without any issue. Now, I tunned some parameters in /etc/my.cnf file. Below are the parameters which I changed.

[mysqld]
key_buffer_size = 298M
max_allowed_packet = 1M
table_open_cache = 64
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 8M
myisam_sort_buffer_size = 64M
thread_cache_size = 50
query_cache_size = 32M
query_cache_limit = 1M
# Try number of CPU's*2 for thread_concurrency
thread_concurrency = 2

and uncommented these variables for InnoDB.In default file, it was commented even INNODB was active.

# Uncomment the following if you are using InnoDB tables
innodb_data_home_dir = /var/lib/mysql
innodb_data_file_path = ibdata1:2000M;ibdata2:10M:autoextend
innodb_log_group_home_dir = /var/lib/mysql
# You can set .._buffer_pool_size up to 50 - 80 %
# of RAM but beware of setting memory usage too high
innodb_buffer_pool_size = 1127M
innodb_additional_mem_pool_size = 20M
# Set .._log_file_size to 25 % of buffer pool size
innodb_log_file_size = 256M
innodb_log_buffer_size = 8M
innodb_flush_log_at_trx_commit = 1
innodb_lock_wait_timeout = 50

Now, to verify whether InnoDB is available or not, I ran show engines command. But, InnoDB is not listed in that. Then, I ran command below command:

mysql> show variables like '%innodb%';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| have_innodb           | NO    |
| ignore_builtin_innodb | OFF   |
+-----------------------+-------+
2 rows in set (0.00 sec)

mysql> show engines;
+------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine     | Support | Comment                                                        | Transactions | XA   | Savepoints |
+------------+---------+----------------------------------------------------------------+--------------+------+------------+
| MyISAM     | DEFAULT | Default engine as of MySQL 3.23 with great performance         | NO           | NO   | NO         |
| MRG_MYISAM | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| BLACKHOLE  | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| CSV        | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| MEMORY     | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| FEDERATED  | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
| ARCHIVE    | YES     | Archive storage engine                                         | NO           | NO   | NO         |
+------------+---------+----------------------------------------------------------------+--------------+------+------------+
7 rows in set (0.00 sec)

I am unable to find where I did the mistake? Can you please help?

Adding the way, issue has been resolved But don't know the way is correct or not!:

Checking error log certainly helped here. On the basis of error log:

InnoDB: Error: data file /var/lib/mysql/ibdata1 is of a different size
InnoDB: 133760 pages (rounded down to MB)
InnoDB: than specified in the .cnf file 128000 pages!
InnoDB: Could not open or create data files.
Then, I commented - #innodb_data_file_path = ibdata1:2000M;ibdata2:10M:autoextend 

After this, I got below error message in error log file:

InnoDB: Error: log file /var/lib/mysql/ib_logfile0 is of different size 0 5242880 bytes
InnoDB: than specified in the .cnf file 0 268435456 bytes!
140430 17:13:37 [ERROR] Plugin 'InnoDB' init function returned error.
140430 17:13:37 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
Then, I commented #innodb_log_file_size = 256M By default #innodb_log_file_size = 5M.

Now, I again started the mysql service and found that Innodb has been loaded as default engine.