Results of the command 'df -h /tmp'

Code: 
root@bravo612 [~]# df -h /tmp
Filesystem            Size  Used Avail Use% Mounted on
/usr/tmpDSK           4.0G  151M  3.6G   4% /tmp
Results of the mySQLtuner.PL

Code: 
 >>  MySQLTuner 1.2.0 - Major Hayden <major@mhtx.net>
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
 >>  Run with '--help' for additional options and output filtering

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.1.63-cll
[OK] Operating on 64-bit architecture

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +Archive -BDB -Federated -InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 168M (Tables: 715)
[!!] Total fragmented tables: 3

-------- Security Recommendations  -------------------------------------------
[OK] All database users have passwords assigned

-------- Performance Metrics -------------------------------------------------
[--] Up for: 1h 50m 16s (291K q [44.134 qps], 9K conn, TX: 531M, RX: 25M)
[--] Reads / Writes: 90% / 10%
[--] Total buffers: 280.0M global + 2.7M per thread (500 max threads)
[OK] Maximum possible memory usage: 1.6G (29% of installed RAM)
[OK] Slow queries: 0% (27/291K)
[OK] Highest usage of available connections: 3% (15/500)
[OK] Key buffer size / total MyISAM indexes: 8.0M/51.8M
[OK] Key buffer hit rate: 99.5% (20M cached / 97K reads)
[OK] Query cache efficiency: 53.0% (119K cached / 225K selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (10 temp sorts / 7K sorts)
[!!] Joins performed without indexes: 115
[OK] Temporary tables created on disk: 22% (1K on disk / 7K total)
[OK] Thread cache hit rate: 99% (15 created / 9K connections)
[!!] Table cache hit rate: 11% (196 open / 1K opened)
[OK] Open file limit used: 14% (370/2K)
[OK] Table locks acquired immediately: 99% (123K immediate / 123K locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
    Run OPTIMIZE TABLE to defragment tables for better performance
    MySQL started within last 24 hours - recommendations may be inaccurate
    Adjust your join queries to always utilize indexes
    Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
    join_buffer_size (> 128.0K, or always use indexes with joins)
    table_cache (> 400)
Yes, i have cleared cache of the browser. On every machine, warnings are shown. But periodically... They are not always present. My traffic made significant fall.

What to do next?