void | NN 3 IE 4 ECMA 1
This unary operator evaluates the expression to its right but returns a value of undefined, even if the expression (such as a function call) evaluates to some value. This operator is commonly used with javascript: pseudo-URLs that invoke functions. If the function returns a value, that value is ignored by the calling expression.
Example
    <a href="javascript: void getSound( );" >...</a>