I dont have IE so I can't see how to fix your problem but I can answer the other two questions:
In the include.php file, at the top there is a piece of code with the HTML headers. If you look through it you will see it linking to a stylesheet called "stylesheet.css". You will need to point this at your own CSS stylesheet. Then you can control how it all looks. Linking to your own stylesheet might fix your current problem.
To add a password and username, you will need to scroll to the bottom of index.php where you will see an ADMIN section. There are two variables that have been set to "CHANGEME". Do what they say and change them to what you want.
In the include.php file, at the top there is a piece of code with the HTML headers. If you look through it you will see it linking to a stylesheet called "stylesheet.css". You will need to point this at your own CSS stylesheet. Then you can control how it all looks. Linking to your own stylesheet might fix your current problem.
To add a password and username, you will need to scroll to the bottom of index.php where you will see an ADMIN section. There are two variables that have been set to "CHANGEME". Do what they say and change them to what you want.