Why does name field change size when making it required?

When I use the full name field and it isn't required, the first and last name span the width of the form, but when I make the full name field required, both boxes shrink.

From what I can tell, it's the extra CSS which was added to the form which is causing this issue. Please replace all of the form's injected CSS with this code and let us know if it helps.

Thanks

If the last name box seems to far away from the first name one, please replace the last rule in my code with the following:

#last_40 {
margin-left: -15px;
}