I've been waiting for Eugene to answer this one as it nor my strong point but I'll give it a shot.
OK
(1) What kind of server are you going to host on? Probably a unix box? If so, change all your .htm files to .php files.
(2) HAve a look at the code of the file you are going to use. Copy all the javascript from the header and save it in a seperate file. copy all css references too. Paste into a file and name it javascriptcss.php.
(3) Delete everything from the top html tag down to and inclding the <body onload... > tag.
(4) Delete everything below and including the </body> tag
Ok what you are left with is a file, suffix.php, with no head and no body tags. We don't need these as the file you are going to isnert this into already has them. OK
(5) Got to the layer you wish to isnert the file into. Open the file you are going to isnert into. and click on insert > script objects > server side include. Choose your file.
(6) Goto the ehader of the file you are inserting the file into. copy all the javascript and css from the layer and paste it into the javascriptcss.phop file. Delete any duplicates of code.
(7) Goto the ehader of the file you are isnerting the other file into, and click oninsert > script objects > server side include and choose javascriptcss.php
press f12
Works for me, probably better ways of doing it.
(6)