Opensource one question after you changed the wording you wanted changed did you click save or did you click save as...Save=right, save as=wrong...plus anytime you change a file make sure you have a copy of it some where.

Make sure the file was saved as a php file if not you can alway's rename the file and make sure it say's php after the period example.

ossn.en.txt = wrong it should look like this: ossn.en.php

That way your browser can read it properly

I edit the page.. now the site is dropping.. nothing is displayed. What will be the possible reason please?

Okay like I said in an earlier post if people would read all of the posts they would find that most of their questions had been answered...But I do have to admit I am lazy at times myself and look for the easy way out.

But to get back to the subject in hand...Here is the link to the post that will answer your question on how to change the Welcome message.

http://community.opensource-socialnetwork.org/discussion/view/407/editing-what-the-front-logon-page-says

Can you tell me exact folder where it lies please?

The general answer to questions like that is:
Get yourself an editor with the ability to traverse all files of a folder (like Notepad++) and do a "Find in files" ...