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.

The rating of TeleNav Inc. (NASDAQ:TNAV) slips from a C to a D. TeleNav provides location-based solutions. The stock gets F’s in Earnings Growth, Earnings Momentum, and Margin Growth. To get an in-depth look at TNAV, get Portfolio Grader’s complete analysis of TNAV stock.

Red Hat (NYSE:RHT) earns a D this week, falling from last week’s grade of C. Red Hat provides open source software solutions that customers are allowed to update, monitor and manage. The trailing PE Ratio for the stock is 58.10. For more information, get Portfolio Grader’s complete analysis of RHT stock.

Taomee Holdings (NYSE:TAOM) gets weaker ratings this week as last week’s C drops to a D. Taomee Holdings produces children’s entertainment. The stock gets F’s in Earnings Surprise and Margin Growth. To get an in-depth look at TAOM, get Portfolio Grader’s complete analysis of TAOM stock.

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.