var Msg=("Do you want to delete the rate: " & dt1 + "-" & dt2 +" = " & rate1.toString());
var Msg=("Do you want to delete the rate: " + dt1 + "-" + dt2 +" = " + rate1.toString());
Can any one tell me the differenc between. I thought there is no difference between + and &. When I type the first code, it doesnot work and when I type second code. It works can anyone let me know what is difference.

There is difference between + and & in vbscript and jscript.

In vbscript:

Operator + sums two numbers.
For example:
result = expression1 + expression2
But if both expressions are strings then concatenate.

Operator & forces string concatenation of two expressions.

In jscript:

Operator + adds the value of one numeric expression to another or concatenates two strings.

Operator & performs a bitwise AND on two expressions.

Thus,your first code is wrong.The & operator in the code performs a bitwise AND.