You were right, I found the styles element that caused the problem. Thanks for the great help.

I tried the above, but my problem is that in contact page not appear textbox and send mail button. I also tried to disable all plugins but the problem remains. At the moment all the plugins are updated to the latest version and wp is the rel. 4.5.2

Yes, I used the iframe tag in the customized url after file name:
“?iframe=true&width=100%&height=100%”
Thanks anyway for the attention you gave me.