I can't understand why my blog's logo is not removing while I have deleted it from themes>images by using ftp. Also there is no any logo option on my theme that I need to disable it manually. I can't understand from which location the logo staying yet and showing on my blog. Is there any way that I can find out where the logo is staying?
Yes, right click on your logo if you're running Google Chrome or Firefox select Inspect Element, this will tell you the path to your logo. If you're running Internet Explorer right click on the image and choose Properties and the path will be displayed.
It is most probably only in the cache, so press CTRL+F5 and check. It it still appears, simply right click on the logo and click on "copy image URL" (if using chrome) or "copy image location" if using firefox. Open file manager and manually change the logo file from that location. Press CTRL+F5 once again to verify the change.