Apparently, there is a way to do 30 day moving average on MSN. As reported as some guy on Phil's blog
Rule #1 Blog: Phil Town on Investing: CHICO'S: CASE STUDY RE: THE IMPORTANCE OF VIRTUAL TRADING
near the end, he says that:
I've found a way to show the 30 day MA on MSN. If you use the MA envelope and change the settings to a 30 day period and 0.00 width, you'll get the 30 day MA.
I am just a beginner, so if someone could confirm this is indeed true, it would help.
Otherwise, just use
StockCharts.com - Simply the Web's Best Stock Charts - it is easy to add 10/30/40 moving average graphs