I have edited some css for the panels in public_html/sites/default/files/ctools/css/xxxx.css file but those changes vanish as soon as i refresh or return back to public_html. So because of that the changes are not taking place.I even changed the permissions in cpanel to 7 7 7 but still the changes are not being saved. Any idea how i shall go about this ?
"public_html/sites/default/files/ctools/css/xxxx.css" - I'm not 100% sure, but I think the files in the /files directory are generated by the ctools module. Sounds like it is overwriting/restoring the file. Copy the styles you need to edit from the ctools stylesheet into your theme's styles.css. This will override the default styling and prevent future issues. Also, it's best not to never edit a module's css files directly. If you ever update the module (which you will), the changes will go poof!
It is best to override the output of any module css in your theme's style.css(sites/all/themes/your_theme/css/style.css) or whatever css you're using. Let me know if it works for you.
I first edited the css in panel's css and it worked.Now i have made the changes to style.css of my theme as clockwood recommended.