unable to do any changes

Hi,
I have got a strange problem in wordpress blog site, whatever changes I am doing to my website backend, it responds fine on my computer but nowhere else. I can’t see the changes or updations which I did in the website anywhere else, I have tried with deleting cookies also and have checked on number of computers.
I have deleted header file from ftp, the page was annoying on my computer and only to those computers where I login to wordpress backend but on the other computers nothing happened means the website is absolutely fine even if I deleted the header file from ftp.
Thats really a strange issue, I have never seen this earlier with any other wordpress website. Kindly suggest as soon as possible.
Thanks,
Preet