remove template formats

How do I remove the page content indent (formatting from the template) by using a code injection..  I'm trying to create a page that pop's up and that I can style differently than my normal template.    I removed the header and the footers,

<style>
  #header, #footer, #preFooter {display: none;}
</style>

but want to move the page content section all the way to the left.  My template pushes it in (centers it).  Does anyone know how to remove that formatting.  

Additionally, is there a way to remove all formatting and just make a blank HTML page popup.  Not ideal, but would be useful to know.  

Hi,
Please share your website URL.

Best,
Leopold

https://www.advinbridge.com/iframe-test

This is the test page where I removed the header, footer, etc. already...