remote access

How do you programme a 3rd party to login and edit data on a website. Hope I have explained it right.

You need to build a CMS. (Content Management System) You can either build one that does exactly what you need using PHP, or you can buy one.

any suggestions on where to get the most reliable and safest CMS?

I am going to recommend building your own...but that is me, and since you are a beginner that might be hard. You could try this.

Not sure which is the best either. I made my own and install it for pretty much all my clients ... custom made.

We are ASP programmers at my company (Windows Only) and our CMS systems are powered by ASP and are 100% custom made. The problem with pre-built CMS systems is that if you don't know how to edit it, and your client asks for a special feature who are you going to turn to to add that feature? That's why creating your own is so much better. Plus you will learn a ton doing it.

Another way for content management is to give them a seperate FTP account to your server. My host gives us unlimited FTP accounts so I can create one for my clients where they can only have access to a certain folder on the website. This makes it where they can upload their text files and I can read them into my content so as to keep the site from being destroyed, but give them the opportunity to change a few things.

TextPattern and WordPress are both nice.