how can I center the whole form on my site? www.strikeaposephotobox.com/questionnaire

how can I center the whole form on
my site? www.strikeaposephotobox.com/questionnaire

You form is setup to show in the center. I checked the page of your site where the form is embedded, and the form appears to the center of the div container you have embedded it, this div container is set to show to the left, that's why the forms appears to the left of the main page.

You could try embedding the following code inside your pages code:

<style>

#primary{

    margin-left: 20%;

}

</style>

Result:

(If it does not work, You should ask your web-designer to center that container. )

I would suggest you to inject the following code inside your jotform to remove the gray background: https://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes 

.supernova{

    background: transparent;

}

Result:

 

Open a new thread if you need anything else, we will be glad to assist you.