how to change signal timing monitor problem

when surfing the Internet the screen goes black with a red box .within this red box the words Attention Signal Frequency is out of range H:89.2 KHz V:110.8HZ Please change signal timing I then press the power button on my Dell Inspiron 530 where I then wait approx 35 seconds before I hear a beep noise then the start button begins to flash. I press the button and my screen comes to life with the message from my Internet provider that computer was in suspend mode please reconnect which I promptly do. the monitor is an old Medion MD7475AC type:EZL15P2