That can be accomplished with a few simple scripts (this is for PDF forms, aka Acroforms):
In the onFocus action, add this JavaScript:
if (event.target.value == event.target.defaultValue) {
event.target.value = "" ;
}
and in the onBlur action, add this JavaScript:
if (event.value == "") {
event.target.value = event.target.defaultValue ;
}
This will blank out the default value, but it will not change anything if there is another value in the field.
Hope this can elp.
Max Wyss.