This week, the overall grades of five Internet and Web Service stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, iPass (NASDAQ:IPAS) falls to a D (“sell”), worse than last week’s grade of C (“hold”). iPass offers enterprise mobility services on a global basis by providing services that simply, smartly and openly facilitate network access from mobile devices while providing the enterprise with visibility and control over their mobile ecosystem. In Portfolio Grader’s specific subcategories of Earnings Revisions, Equity, and Sales Growth, IPAS also gets an F. To get an in-depth look at IPAS, get Portfolio Grader’s complete analysis of IPAS stock.

This week, Liquidity Services (NASDAQ:LQDT) drops from C to a D rating. Liquidity Services provides full service solutions to market and sell surplus assets and wholesale goods. The stock also rates an F in Earnings Momentum. As of March 1, 2013, 20.2% of outstanding Liquidity Services shares were held short. For a full analysis of LQDT stock, visit Portfolio Grader.

Velti (NASDAQ:VELT) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Velti is a global provider of mobile marketing and advertising solutions. The stock gets F’s in Earnings Growth and Earnings Momentum. For more information, get Portfolio Grader’s complete analysis of VELT stock.

This week, Youku Tudou Inc. ADR’s (NYSE:YOKU) rating worsens to a D from the company’s C rating a week ago. Youku.com operates as an Internet television company in the People’s Republic of China. The stock gets F’s in Earnings Revisions and Equity. The stock price has dropped 11.3% over the past month, worse than the 0.8% increase the S&P 500 has seen over the same period of time. For a full analysis of YOKU stock, visit Portfolio Grader.

The rating of 21Vianet Group (NASDAQ:VNET) declines this week from C to a D. 21Vianet Group provides carrier-neutral Internet data center services in the People’s Republic of China. The stock gets F’s in Earnings Growth and Earnings Momentum. The trailing PE Ratio for the stock is 253.40. To get an in-depth look at VNET, get Portfolio Grader’s complete analysis of VNET 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.