LogIn Error

I am new to WordPress but have a website up and running.

I do not use a server / FTP / etc. to make changes to my website. I have solely been using the Twenty Ten Weaver theme options and making changes to my website using the WordPress dashboard.

When I upgraded my theme, I can no longer login to WordPress at all. I’m receiving the “Headers already sent” messages and would love to look at the “functions.php” file to fix the issue on line 205… But I’m unable to login in to the dashboard to even see that file!!

If you have any advice for a WordPress novice – thank you so much!!