There are two aspects here.
1. If you want just one place to change styles like font colors, underlining of links, background colors, margins and padding and so on, use a separate stylesheet which is linked to in all the pages. See http://www.wickham43.supanet.com/tut...raladvice.html
2. If you want the arrangement to be a standard by having divs or tables in certain places in each page you need a template. (2c is recommended.)
2a. You can have a basic page which just shows the header, navigation menu, content space and footer and save this as template.html. This seems to be what you are doing now. You then open the template, add content and save as content1.html , add different content to the template and save as content2.html but as you have discovered, if you want the change the framework you have to change the template and then change all the pages.
2b. You use a Frameset which has the header, footer and menu but also has a frame where you want content to change. This is fed from different html pages which only have the different content. This method is old and not recommended by experts but still simple and in common use.
2c. Use PHP scripting. This is similar to framesets in that it has a template with the header, footer and menu but has PHP code where you want different content inserted. This is in separate "include" files which don't have any html tags, head content, nothing except just the code for the content. This is inserted by your host's server before downloading by the viewer. You need to check that your host supports PHP as cheaper contracts do not. You also need to learn PHP and look at the server-side scripting board on this forum.
Or you do it the other way round by having the header, footer and menu as PHP includes on each content page; it's probably better like this.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.