@prakamya: It is part of your task to investigate and find out. :) Please see https://www.mediawiki.org/wiki/How_to_become_a_MediaWiki_hacker#Feedback.2C_questions_and_support . If you have specific questions, please ask them - we are happy to help!
The browser used should be irrelevant here.
extensionsimages/ might be due to a missing / somewhere in the code (imageDir or such?), as I can imagine this to be extensions/images/ instead.