IE
1. Tools > Internet Options.
2. Security tab.
3. Internet.
4. Custom Level.
5. Scripting.
6. Active Scripting > Enable > OK.
7. Yes > OK > F5


FF
1. Tools > Options.
2. Content.
3. Enable Javascript.
4. OK > F5


Opera
1. Tools > Preferences...
2. Advanced.
3. Content.
4. Enable Javascript .
5. OK > F5


Note: Tắt thì các bạn chỉ cần chọn vào Disable thôi nhé