I can't tell that I catch what you mean, but I will answer in general manner
1- if you are building the whole site from scratch: You can create your site by any CMS like dotNetNuke or joomla which will allow you to login and edit what you want
2- if you are building just this page from scratch : You can build your page with online-editing in mind, in this case I recommend to build two pages one for for viewing content and the other for online-editing you can use any HTML-Editor control like FCKEditor
3- if you are dealing with already built page : it will be easier to build administration page which you can upload the new version of the content page to it, and the administration page take care of replacing the content page
hope this can help you, if not, please feel free to clear your needs so we can help more