Guys I am having below CSS in the head tag of an aspx file which I want to use only for one particular page in the site. If I put this code in master page in .net then it will be applied to all site pages which I do not want. How do I make the below css work only for one particular page. That page is having the body id = “mainpage”
That makes most of your answer nice and easy you should simply insert the body ID into all the rules (in their place in the tree) this is called "specificity" in other words you are going to make those rules so specific they will only apply to pages with that ID in them.
* html body#mainpage #mainpage table#header #mainpage .fixedelement
You have however a rule for the <html> element,
* html, which you cannot target this way as you cannot target parents based on their children - the <body> with the ID is a child of the <html>
so if it's important to target that rule, is it possible you can put pages unique ID's onto the <html> element instead - or if there are wrapper divs already in place move everything down a level in the code?