Internal Server Error

This is a server configuration issue, it seems. Check your logs and ask the host. Perhaps there is mod_security or anitger layer of protection that doesn't like the file.

The values showing are much larger (post_max_size 21 GB, upload_max_filesize 2 GB). Are you sure that you entered the correct values in .htaccess and/or php.ini? With the current values the server error might occur because the server just has not enough resources available for the configured limits.

Try it with

php_value post_max_size 260M
php_value upload_max_filesize 128M

in .htaccess (The "M" is to be used for megabytes and easier to handle than providing the values in bytes). If you made any changes in php.ini you should restore the original values (or set the same limits in "M" there). Do you see the correct limits then?

# limit the maximum memory consumed by the php script to 64M

php_value memory_limit 200M

# register_globals is deprecated as of PHP 5.3.0 - disable it for security reasons.

php_value register_globals 0

# post_max_size is the maximum size of ALL the data that is POST'ed to php at a time (260 MB)

php_value post_max_size 260M

# upload_max_filesize is the maximum size of a single uploaded file (128 MB)

php_value upload_max_filesize 128M

php_value max_execution_time 300

php_value max_input_time 300

# on development servers, set to 1 to display errors. Set to 0 on production servers.

php_value display_errors 0

</IfModule>

php_value memory_limit 200M

php_value post_max_size 260M

php_value upload_max_filesize 128M

############################
# COMPRESSION

# Turn on mod_gzip if available
<IfModule mod_gzip.c>
  mod_gzip_on yes
  mod_gzip_dechunk yes
  mod_gzip_keep_workfiles No
  mod_gzip_minimum_file_size 30000
  mod_gzip_maximum_file_size 30000000
  mod_gzip_maximum_inmem_size 30000000
  mod_gzip_item_include mime ^text/.*
  mod_gzip_item_include mime ^application/javascript$
  mod_gzip_item_include mime ^application/x-javascript$
  # Exclude old browsers and images since IE has trouble with this
  mod_gzip_item_exclude reqheader "User-Agent: .*Mozilla/4\..*\["
  mod_gzip_item_exclude mime ^image/.*

Add the values only once inside the <IfModule mod_php5.c> block.

did you mean to delete this lines

# upload_max_filesize is the maximum size of a single uploaded file (128 MB)

# post_max_size is the maximum size of ALL the data that is POST'ed to php at a time (260 MB) 

or

this

</IfModule>

php_value memory_limit 200M

php_value post_max_size 260M

php_value upload_max_filesize 128M

The lines with php_value after </IfModule>.

no changes after removing this lines ...a 500 Internal Server Error error

If the problem started after modifying .htaccess and/or php.ini, you have most likely made a faulty modification. Compare your current files with the original files or a backup if available to find out what's different and fix the issue.

Or maybe there's some entry in the server logs that might explain what's currently wrong causing the server error. If the error logged gives some indication about the cause, you can fix it.

Or maybe you saved the modified files with wrong encoding (i.e. with Byte Order Marks - BOMs - which are invisible characters at the beginning of the file causing problems). In this case save the files again with UTF-8 encoding without BOMs or restore the original files for not to get rid of the server error at least.

the problem isnot started after modifing htacess file .how can I check error logs?thank you for your help.

in error log file ...I found metatags plugin error