Was the Issue with Caching?

I have an ASP.NET Website with a few changes made to the fields on a web Page. I actually made few fields mandatory which were optional before. And published the changes to the Production.
Now, a user is not able to see the change and can submit the form with the changed field as optional field. i.e. I have made a chnage to field X to make it mandatory which was previously optional. Now the user is seeing and able to submit the page as x is optional. Now, can I say that the user is having a problem of browser is loading the ASP.NET  web site Page from Cache?  Will disabling cache in IIS (At Application level)fix my Issue? Though I understand it incurs a Performace cost. I really wanna know if this fixes the Issue and this is the problem.

Thanks,
Pavan.