This week, the ratings of four Software stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, SRS Labs (NASDAQ:SRSL) falls to a D (“sell”), worse than last week’s grade of C (“hold”). SRS Labs develops and licenses audio and voice enhancement technologies. In Portfolio Grader’s specific subcategories of Earnings Growth and Margin Growth, SRSL also gets F’s. For a full analysis of SRSL stock, visit Portfolio Grader.

TeleNav Inc. (NASDAQ:TNAV) earns a D this week, falling from last week’s grade of C. TeleNav provides location-based solutions. The stock gets F’s in Earnings Growth, Earnings Momentum, and Margin Growth. For more information, get Portfolio Grader’s complete analysis of TNAV stock.

This week, Red Hat (NYSE:RHT) drops from a C to a D rating. Red Hat provides open source software solutions that customers are allowed to update, monitor and manage. The stock price has fallen 6.8% over the past month, worse than the 1.7% decrease the S&P 500 has seen over the same period of time. The stock’s trailing PE Ratio is 60.60. To get an in-depth look at RHT, get Portfolio Grader’s complete analysis of RHT stock.

This week, Taomee Holdings’ (NYSE:TAOM) rating worsens to a D from the company’s C rating a week ago. Taomee Holdings produces children’s entertainment. The stock gets F’s in Earnings Surprise and Margin Growth. For a full analysis of TAOM stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.