I ended up following solution which worked out for me.
For another app which i am integrating, i made its whole body into a container and gave a class to it.
In layout of another app,
<!-- Another application body layout-->
<body>
<div class="another-app-container">
<!-- Here goes whole layout of page -->
<p class='someClass' > ....
<div class='myClass'> </div>
</p>
</div>
</body
In CSS of that app, i applied following CSS rule,
.another-app-container * .someclass{
// CSS rule goes here
}
.another-app-container * .myClass {
// CSS rule goes here
}
Beauty of CSS i got here is, '*' which applied the CSS rules even it has lot of nesting of elements CSS.
So, it segregated the CSS for my own from another application