Thank you for the information webgalli. But i didnt get you when you said something about writing plugins as per guidelines.
Can't i use my individual innovations?

@Newbie - be as innovative as you like!  What Webgalli is saying, is to read through the documentation on plugins first, it'll make your experience a whole lot better.  Also, you are absolutely free to modify the core engine if you want, but it's not recommended for a number of reasons:

1. It breaks upgrade paths - you will lose your customizations if you attempt to upgrade your elgg version
2. Subtle nuances that you may not be aware of can ripple through the system - elgg uses a *very* normalized database structure so if you create/delete something out of place it can be hard to track down
3. If something does break in a customized system noone in the community can provide any decent help
4. It's very rarely necessary - pretty much anything you want to do can be achieved in a plugin while leaving the code base intact

north east ? kolkata ? উত্তর পূর্ব? আপনার কলকাতা? ? which college ? my elgg-friend from kolkta is at college in chennai for comp sci...;-)

...i cant install any other themes other than the default

What happens when you try?

i wish to replace my site title with an image{logo}

Have a look at views/default/page/elements/header_logo.php and the css class .elgg-heading-site in views/default/css/elements/typography.php

Thanks a lot gillie! I have worked out my problem with your direction. Is there anyway i can change the topbar height?{not the header}