Is it possible to display a custom HTML page in a survey after the welcome screen but before questions?
If so, how?

Depends on what you understand under custom HTML question.
You can use a textdisplay question to display your own HTML content.

Thank you for your answer, i do not want to add a custom question, i want to add a new page.

I do not want to display the html code.

Quick answer : no ....

Maybe plugin can help you

But :

> Is it possible to display a custom HTML page in a survey after the welcome screen but before questions?
VS
> I do not want to display the html code.

You are really unclear ....

What do you exactly want to show? As Denis said, you are not very clear. Do you want to start the survey, then put a totally unrelated html page (no survey layout at all) and then go back to Limesurvey? Because you would at least need to display the button to move forward from your custom HTML page. So please, be more specific, otherwise it will be very difficult to help you. I could for example imagine the suggested text display question that Jelo mentioned and maybe use a frame to embed the html page. But as we don't really know what you are trying to do, this is all guesswork.