If users enter more digits than the Shopping Cart's Quantity column is set for the math goes crazy. To see this behavior go to http://www.flowtronexparts.com/html/electricalcircuitbreakers.htm and enter more than four digits (say, eight) in the 1st item's Quantity field. Then go to the Shopping Cart and see that the total is not correct.
Why can't limit (like with a standard HTML text field) the number of digits the text field will allow?
Another question - In the same Add To Cart function why does the "Added to cart" pop-up dialog window have "Warning: applet window" in the lower left corner?
FYI: The problem you are seeing with the total is due to a known problem with formatting the price when the prices get into exponential figures (extremely high prices). The priority on that fix is low as it is not practicle that people will be placing orders upwards of $1 billion in the shopping cart.