Wordpress Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 72 bytes) in /wp-includes/meta.php on line 837

[admin]

I am new in wordpress. i am getting below error.

<blockquote>
Fatal error: Allowed memory size of 268435456 bytes exhausted (tried
to allocate 72 bytes) in
/wp-includes/meta.php on line 837
</blockquote>

while accessing new post page. and also i have added below code in htaccess file.

<IfModule mod_php5.c>
php_value memory_limit 512M
</IfModule>

Please help me to sort out this issue.