i am working in windows 7 64 bit
form builder 10.12.0.2 32 bit
You are using an unsupported combination. See MOS Doc ID 1386014.1
my default browser is Google Chrome
The above said, did you try other browsers ?
You can also refer to this OTN reference:
1. I would not recommend using Forms 10.1.2.0 with Oracle DB 11.2.x. Patching Oracle Forms to 10.1.2.3 would be recommended. Using version Forms 11 would be better.
2. Attempting to use the Developer Tools on Windows 7 is not a great idea although it can be made to work. Developer Suite 10 is no longer supported and was never really intended for use on Win7. Again, patching to 10.1.2.3 is recommended and required if you plan to follow the Oracle instructions and certifications.
3. Installing the Forms Builder (Developer Suite) on Win7-64bit is not at all certified and was never supported.
4. Using Java 7 was not certified and therefore not supported for use with Forms 10.x
In general, Forms 10.1.2.x has been desupported. Customer using this version or older should be working on a migration plan for getting to the latest supported version which is 188.8.131.52.