6
The theme.html file, not style.css file.
Locate where the login form is and check if login and search are connected. There are several themes having the two on the same line.
If you could not figure it out yourself, feel free to post the login and search parts here, and please not the whole file. Also please delete the pasted css file as well (it takes too much space and creates distraction for other users). Thank you.
[edit] Another way of checking it - compare your modified theme.html file against the original.[/edit]