What exactly do you want to be fixed? The header image? The blog title? Navigation menu?

This will most likely be done with CSS, which makes this more of a evoskin & template question. But the answer will depend on what you want to remain stationary.

Thank you so much for responding.. What I mean is let's say we have perticular topic, we want to keep few lines explaining that category and all the post goes under that. Few lines stays consistent for that categories.. For example http://blog.milestoneinternet.com
I have several categories such as email marketing etc.. Any way, my goal is I can have an option to keep few lines consistent for each category before we have all the post under that.
I realy appreciate help