Sql Startup Strings?

My banner advertising business is ran by mysql database. The problem that I am having is that the database is getting larger each day and is causing the site to slow down, banners to load slowly, etc...

I have been experimenting with startup strings and some of them work great for about 24 hours and then the same thing happens all over again.

My current start up connection is at:

nohup ./safe_mysqld --socket=/tmp/mysql.sock --port=3306 -O key_buffer=256M -O sort_buffer=8M -O record_buffer=8M -O back_log=40 -O max_connections=700 -O table_cache=6000 &

Any help, suggestions, etc would be greatly appreciated.

Thank You