You'll want to look at some CMS systems, there are a load of opensource ones out there. Wordpress is great for beginners, Joomla and Drupal are a bit more advanced, that's just to name a few. There are some other, more simple, ones, like cushyCMS and simpleCMS, which may be of more use to you. But all of them will involve you having some sort of php knowledge and a mySQL database. Good luck!
you cannot create admin control panel just with html and css, you need some server side technologies like asp, php , asp.net rather you can go with readymade CMS with control panel like joomla, drupal
You can learn to code PHP and create an admin panel or you could just use something like WordPress. I use WordPress for all of my sites and it works great but I've also created my own admin panel from PHP. If you don't know PHP however, it may take awhile to learn so it's probably not the best option. If you want to attempt to learn PHP I suggest visiting http://www.tizag.com or http://www.w3schools.com
Yes, as stated you don't want to start from scratch unless you are an experienced programmer and the available CMS's don't do what you want. I suggest Joomla for your needs. Mark
First, I think you have to set permission to who can access your Admin control panel, then you can make a form to easy submitting your post. What ever it is, you have to know php or some program script. Because it not just the matter of CSS/HMTL, and it's related to database.