If you are running a web application on 64-bit machine and if the web application is using Oracle.DataAccess assembly, then you may receive this error:

Could not load file or assembly 'Oracle.DataAccess' or one of its dependencies. An attempt was made to load a program with an incorrect format.

To fix this error, you will need to go to your IIS manager and locate the application pool that the web application is using, then right-click the application pool, and go to Advanced Settings, then set “Enable 32-bit Applications” to true. After this, your web application should be running fine.

Hope this helps.