I always make a change on my own CSS layout for so many times

but my always problem is about some of my CSS codes is not working

and i thinking its might because of putting a lot of codes in that file

i cant think of any solution that might fixed it, sometimes i make it even worst

so my question is: when you put a lot a codes/tricks on your layouts code,
can some of your codes will not gonna work as well,

and how may i prevent this? :thunder:
can someone help about this question...
thnks