MSIE 7 does not support the javascript reserved keyword const used to define constants.

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Firefox 2, Safari 2, Safari 3.0.2, Opera 9, NS 6.1, NS 6.2, NS 7.0, NS 7.2 and many browsers support the javascript reserved keyword const to declare constants in javascript application.

Reference: reserved keyword const: "You can create a read-only, named constant with the const keyword. The syntax of a constant identifier is the same as for a variable identifier: it must start with a letter or underscore and can contain alphabetic, numeric, or underscore characters."