Maybe the word "mode" isn't the right choice. I'm not talking about a vibrational mode, but rather the low-frequency thermal expansion of the table. I find it hard to believe that the perimeter of the table won't change by more than 10-10 m or so over 1-10 mHz timescales.
Regarding the AC on/off spectrum, do you mean a spectrum of the gyro signal, or some other configuration?
I have a feeling that Alastair will know better what to do about the windows, but I can try and think of something in his absence.
About the word wrapping, I don't know; I've never had an issue in Safari (OS X) or Firefox (Linux).
I don't think there's any breathing mode being excited. At low frequencies, we are most likely measuring the air noise. Since the table has its first eigenfrequency above 100 Hz, the flexing at 100 mHz is suppressed by a factor of lots.
Most likely, we just need to plug the giant holes on that box. Where are those windows??? Also, take a spectrum with the AC turned off and make a comparison with it on/off.
P.S. Why do the entries in this elog not word-wrap in some browsers, while the ones in the TCS lab tab do word wrap?