I would like the know in what cpus % can be considered in save range and also load average? Which indication will give signal something is wrong with the server?

top - 22:55:51 up 3 days,  6:39,  1 user,  load average: 0.53, 0.43, 0.37
Tasks: 229 total,   2 running, 227 sleeping,   0 stopped,   0 zombie
Cpu0  : 16.2%us,  0.7%sy,  0.0%ni, 82.8%id,  0.0%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu1  : 10.5%us,  0.7%sy,  0.0%ni, 88.5%id,  0.0%wa,  0.0%hi,  0.3%si,  0.0%st
Cpu2  :  9.0%us,  0.0%sy,  0.0%ni, 91.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu3  :  0.3%us,  0.3%sy,  0.0%ni, 99.4%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu4  :  1.0%us,  0.0%sy,  0.0%ni, 99.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Cpu5  : 44.8%us,  2.6%sy,  0.0%ni, 37.0%id,  0.0%wa,  9.4%hi,  6.2%si,  0.0%st
Cpu6  :  3.0%us,  0.0%sy,  0.0%ni, 96.7%id,  0.0%wa,  0.0%hi,  0.4%si,  0.0%st
Cpu7  :  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  16468596k total,  2423908k used, 14044688k free,   200172k buffers