HTML MIstake

if Default scroll is not working
give  overflow: scroll;
for the whole content

In JavaScript the function name should not begin with
close()
open()
because there is  already in build functions

 If two css is applied to a same html entities then you may occur a problem

Example scenario:
 If you applied css to list as in common as  li and
again you are creating a class or id    #header li  or .header li

this may occur during editing others code