SSI Help!

Not sure were else to put this but maybe someone can help. I want to add a header and footer to pages using SSI. I am using and have even tried . This works for pages that are in the same dir as the .txt file (i.e. /www/webpage files and .txt files here/). If I try and add the SSI into a page that is in another dir it doesn't work (i.e. /www/dir2/webpages here). I have also put the full path and even tried the full web URL without luck.

Can these .txt files only be include if they are in the same dir as the web page they are being included in?

Thanks ahead of time!