The HTML displayed is stored in easy-to-edit template files. They are found in the folder:
For HTML files with a lot of displayed text in them -- like the search tips page -- separate templates are maintained for each language, in subfolders like "english" and "german". For files that don't display their own text -- like the stylesheet "style.inc" -- a single file is used in the base templates folder.
Edit your templates to match the look and feel of the rest of your site (you can use include files to make things easier, too).
When upgrading to new versions of FDSE, the automatic installer will not overwrite your template files, so your changes will be protected. When doing manual upgrades, make sure you do not overwrite any templates you have customized.
"Customizing HTML" https://www.xav.com/scripts/search/help/1021.html