the headers already sent error means that there is pout put on the page before the Session is started.
where it is reporting the issue at line 1, it most likely means that the Include Unicode signature (BOM) option has been set on your page.
Go to Modify -> Page Properties. In the Title / Encoding Section uncheck the Include Unicode signature (BOM) option.
to be able to tell what is wrong with the layout, I would need to seer the issue in the browser.