ST_Distance Issue

I am calculating distance from my current location with all available regions(polygons) in my table.
I am using ST_Distance method for this.
My regions are stored with SRID = 900913.

Distance for point in Europe from USA region is coming as 122.78.
How come this possible. These regions are so far.

Here is my query. Can you please suggest me how can I get actual distance in meters here.

SELECT distance
(st_geomfromtext('point(-123.574219125 47.8131546948944 0)', 900913),
st_geomfromtext('LINESTRING(-0.791015625 48.4874864798841,9.4921875 54.5975278521139,27.59765625 55.3541353102106,36.38671875 48.3124279040718,22.32421875 40.3465441211801,5.888671875 43.8662180065564,-0.791015625 48.4874864798841)', 900913)
)

Query returns 122.785055218779

What is significance of SRID here. Am I missing something?
Which SRID should we use for general purpose.

Thanks,
Archana Ghag
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email: archana_ghag(at)infosys(dot)com<mailto:archana_ghag(at)infosys(dot)com>

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