Performance and javascript issue in a drupal 7 website I have a drupal 7 website. Currently its performance is not good and takes much time to render the web pages. For performance, I checked out in YSlow and came up with some results like move all js files at bottom, compress them and images too etc.

As far as I know its drupal structure to render js first at the head and then it loads the body content. So, Is there any way to move all js files at bottom of the web page in drupal???

I tried to aggregate javascript and css files with the admin panel in drupal but that is breaking some features of the website, say for example, some jquery and ajax codes are not working. Please suggest something for these problems as how can I approach for it.
You could try advagg, but shoving cloudflare at the problem is usually easier, let them deal with the js complexity by converting it to rocketscript for you for free!

Or you could mention which modules you have, how many scripts you are attempting to load, whether they are asynchronous/deferred etc, what version of jQuery, perhaps even a link to the site itself so we can have a look?