How to optimize my MySQL query to use less mysql connection?

I am getting database error via email. Please let me know, How to fixing on this issue?

Is my default settings, max_connections=800 and max_user_connections = 50, I wonder what is good parameter to set for max_user_connection for VPS?

Code:

Database error in vBulletin :
mysqli_real_connect(): (42000/1203): User nadda_data already has more than 'max_user_connections' active connections

User nadda_userdata already has more than 'max_user_connections' active connections

 

Please can you let me know, How to optimize my MySQL query to use less mysql connection? what is good parameter to set for optimize?

This is my default my.cnf settings.

Code:

[mysqld]
local-infile=0

max_connections=800
max_user_connections = 50
datadir="/var/lib/mysql"
socket          = "/var/lib/mysql/mysql.sock"

key_buffer = 256M
table_cache = 28560
open_files_limit=50000
join_buffer_size = 2M
read_buffer_size = 2M
sort_buffer_size = 6M
tmp_table_size=128M
read_rnd_buffer_size=4M
max_heap_table_size=64M
myisam_sort_buffer_size=64M
thread_cache_size=8
thread_cache=512
query_cache_limit=12M
query_cache_size=256M
thread_concurrency = 8
wait_timeout=1000
connect_timeout=1000
interactive_timeout=1000
#log-slow-queries = /var/log/mysqlslowqueries.log
max_allowed_packet=268435456

default-storage-engine=MyISAM
innodb_file_per_table=1
[isamchk]
key_buffer =64M
sort_buffer_size = 64M
read_buffer = 16M
write_buffer = 16M

[myisamchk]
key_buffer = 64M
sort_buffer_size = 64M
read_buffer = 16M
write_buffer = 16M

[mysqlhotcopy]
interactive-timeout
[mysqld_safe]

log-error="/var/log/mysqld.log"