I use bootstrap for front-end development. But sometimes i faces some problem like positionig,margin and padding .Some of the browser doesn't support this like some features are unavailable for ie7 or ie6 etc. There are two types of layout here and both are responsive.They are fixed layout and the other one is fluid. I need to know the very basic of it. When and why I use row or row-fluid?
You use the fixed layout if you want your website to have a fixed width. If you use the fluid layout the website width will stretch to fit your browser window. Check more here http://stackoverflow.com/questions/9780333/fluid-or-fixed-grid-system-in-responsive-design-based-on-twitter-bootstrap
Fixed layouts are always going to be better not just for the simple reason that people dont want to have to scroll, but also because of the issues with different browsers
I think you have that backwards -- in fact that's one of the DUMBEST things I've heard in quite some time. Fixed width layouts are inaccessible rubbish sleazed out by lazy developers who usually don't know the first thing about building a website properly. Though the same can be said for idiotic CSS framework garbage like bootstrap -- for which developers are dumber for it even existing. If you 'need' bootstrap (or YUI, or jQuery, or Mootools, or Blueprint) to make a website, or find any advantages to using it, you should probably back the **** away from the keyboard and take up something a bit less dangerous like macramé. My advice, as per every time the subject comes up, is to throw bootstrap in the trash and start over with *SHOCK* content of value marked up semantically, to which one uses just plain CSS to apply an elastic, semi-fluid AND responsive layout. Anything else is halfwit sleazy shortcuts that will bite you in the ass and result in a inaccessible slow painful to use steaming pile!