Entire page shifts to left on iPhone

your site has some validation errors which might (or might not) have anything to do with your problem:
http://validator.w3.org/check?uri=http%3A%2F%2Fwww.thuvaemilie.com%2F&charset=%28detect+automatically%29&doctype=Inline&group=0

http://codex.wordpress.org/Validating_a_Website

using fixed width values in a ‘responsive’ theme (as you have done at least for the styles of #primary, #content, and #secondary) can also be the cause for problems in narrower browsers; unless this is compensated in the @media queries in the stylesheet.