I want to count total no of links in a page and click one by one

[excellentpawan]

This is expected because when we create a reference to the object and use it for the first time, QTP cashes the object and maps it to the run time object.It does this cashing to improve performance on the same object when used later.But when the application state has changed(page refreshed or changed) these object references are no longer valid.So I would suggest you to get the reference again before you click.
This is how you would do it.

Code:

Set objlink = description.Create()
objlink("micclass").value ="Link"
set links = browser("title:=.*").Page("title:=.*").ChildObjects(objlink)
totalnooflinks = links.count
For i =0 to links.count -1
    set links = browser("title:=.*").Page("title:=.*").ChildObjects(objlink)
    links(i).click
    browser("title:=.*").Back
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