Electret microphone weird offset problem
The electret microphone has a FET buffer inside of it and has a DC offset. The capacitor blocks the offset, however you need a path for the bias current of the op-amp. Bias current is a current flowing into or out of the op-amp input. The capacitor also blocks that voltage, so it will tend to float up towards one rail or the other rail depending on the op-amp. A resistor to ground is the usual way to provide that path. 

The pole formed by the capacitor and the resistor to ground gives you low frequency roll-off. So if you use a 100K resistor to ground and a 0.1uF (100nF) capacitor the response will be -3dB at 16Hz. If your op-amp has a bias current of 100nA then the input offset due to the 100K resistor will be 10mV (the op-amp will have a bit of offset voltage in addition, which may add or subtract from that). If you match the resistances seen at the inputs the total input offset may be less if the input bias currents are well matched, however that's not always necessary or desirable. 







simulate this circuit &ndash; Schematic created using CircuitLab



The LM741 has a typical input bias current of 80nA at room temperature (though it can be as much as 1.5uA under extreme conditions). 80nA * 100K is 8mV. The op-amp has an offset of typically +/-1mV so the typical output offset with your gain of 11 should be less than 100mV at room temperature.