Customise Dynamics Portal Sign In Page. Hide existing Sign In Controls.

Hi.

I am trying to customise the Sign In Page for the Portal.

I have done some investigation and I can add HTML, CSS and jquery by creating a content snippet: Account/SignIn/PageCopy

I am hiding the existing controls (username, password) via jQuery. 

But is there a way to hide it from the very start of loadup?

The reason I ask is because for a brief second, you can see the div when the page is loading, and then hides when the page is fully loaded.

It looks unprofessional.