Please try to add navigation link for logo too. It seems that when clicking on logo it does not navigate anywhere.
Since most users prefer clicking on logo for navigating to home page, try to add them.
The Create Challan and Print Challan button will look good if you make it smaller and put them horizontally instead of vertically. Just name the buttons Create and Print.
In the User Registration page, the confirmation popup shows "Your Message has been successfully submitted", you are not sending message here. Make it say "Successfully registered!" or something like that.
Please check out the drop-down menu in User Login section, it is hidden inside the Navigation.
Fix the issue and bring all the drop-down content forward.
Problem:
There is little problem in your admin login page where if the user leaves the field empty it is still showing incorrect username and password.
Solution:
Add both of the field as required field so if the user leaves any of the field empty a message like "required" or vice versa should display on the screen.
The space in the top of heading is little big. You need to decrease that.
In the label name the font size is little big and need more spacing between label and input field.
In the footer copyright part, the background color is not matching with the design color code, it should be #00031E.
The spacing and font are not properly created and aligned.