Site looks different when I redirect

I have set up a site in Dutch for The Netherlands. The site is located at https://www.yanover.nl

I have redirected the url https://www.nedbrit.nl to https://www.yanover.nl When I look at the site via https://www.yanover.nl it looks ok but when I use https://www.nedbrit.nl the site look different.

Testing has shown that this occurs with users if Internet Explorer. If I use Firefox in my test the site appears to be ok.

It is baffeling me and I would apreciate suggestions and information to solve this issue. Thanks.