Standard&Poor's Ratings Services revised its outlook on Westfield, Mass.' 'A+' GO bond rating to negative from stable following significant depletion of the general and stabilization funds over the past four fiscal years, for various costly onetime expenditures, leaving the city open to exposure during a time of statewide financial concern. At the same time, Standard&Poor's assigned its 'A+' rating to Westfield's new $12.48 million GO bonds, reflecting the city's: Modestly growing and primarily residential tax base, with a mix of industrial and commercial sectors; Continued moderate tax base growth; Unemployment rates, which that have remained below commonwealth and national levels through the current economic slowdown; and Income levels that have historically tracked the nation's averages. The