Each weekday, TheStreet.com Ratings updates its ratings on the stocks it covers. The proprietary ratings model projects a stock's total return potential over a 12-month period, including both price appreciation and dividends. Buy, hold or sell ratings designate how the Ratings group expects these stocks to perform against a general benchmark of the equities market and interest rates.

While the ratings model is quantitative, it uses both subjective and objective elements. For instance, subjective elements include expected equities market returns, future interest rates, implied industry outlook and company earnings forecasts. Objective elements include volatility of past operating revenue, financial strength and company cash flows.

Homebuilder

Toll Brothers

(TOL) - Get Report

has been downgraded to hold from buy. The company's earnings per share fell 79.3% in the most recent quarter when compared with the year-earlier period. Return on equity is just 12.4%, well below the industry average of 17.1%. Toll Brothers had been rated a buy since December 2006.

Cognos

(COGN)

has been downgraded to hold from buy. The company is a developer of information technology software. TheStreet.com Ratings finds that Cognos' cash flow from its operations has been weak overall. Net operating cash flow decreased to $29.9 million in the first quarter of fiscal 2007, down 58.9% from the same quarter last year. COGN had been rated a buy since April 2007.

Another information technology firm,

Insightful

(IFUL)

, has been downgraded to sell from hold. The company lost 9 cents per share in the first quarter of fiscal 2007 after losing 3 cents a share in Q1 2006. Insightful currently has a negative return on equity of 8.4%, well below the industry average. IFUL had been rated a hold since August 2006.

Tax preparer

Jackson-Hewitt

(JTX)

has been upgraded to buy from hold. The company's 1% revenue growth in the fourth quarter of fiscal 2006 compared with Q4 2005 actually outpaced the industry average of 0.8% during that same time period. Earnings per share have increased significantly in the past fiscal year, jumping 25.3%. TheStreet.com Ratings expects this trend to continue. JTX had been rated a hold since April 2007.

Sports apparel company

Ashworth

(ASHW)

has been downgraded to sell from hold. TheStreet.com Ratings sees multiple weaknesses in this company, including deteriorating net income, disappointing return on equity, weak operating cash flow and feeble growth in earnings per share. The company's stock price is down 15.9% over the past year. Ashworth had been rated a hold since September 2005.

Spherix

(SPEX) - Get Report

has been upgraded to hold from sell. The company's biotechnology division has developed pollution tests and even life-detection systems for experiments on Mars. Spherix also runs an information services unit that operates contact centers for government agencies. The company appears to have the ability to cover short-term cash needs, and its 0.02 debt-to-equity ratio is very low. Shares of SPEX are up 14.4% over the past year, and yet the company still trades at a significant discount to its peers. Spherix had been rated a sell since June 2005.