Well as Kyttias explained, these are notices, not fatal errors, they are usually disabled on webhosts. However, the presence of notice errors can be useful for debugging, so maybe leaving them on is not a bad idea if you want to create custom scripts or to edit the script. You can disable/enable notice error on a per-page basis, so for whatever page you edit, leave them on and they may be able to help you detect bugs such as typos and failing to initialize a variable.
Also you can try out mysidiahost.com, which is a webhosting service I provide and it is free:
http://mysidiahost.com/