How to change a link in a css webtemplate for all pages simultaniously?

working in cs4How to change a link in a css webtemplate for all pages simultaniously?You should research using php includes if trying to hand code. Need to know which program you are using to edit the template with if you want to know how to. Most templates will have header.html and footer.html that you can change once and will show on all pages hope that helps