I want to use different CSS files for different browser types. Is there any simple HTML code which can detect different types of browsers and include CSS files accordingly?<
It is usually easier to use 'hacks' within the same stylesheet.
This is not to condone their use (as I don't want to be modded down by evangelists :))
http://www.webmonkey.com/tutorial/Browser-Specific_CSS_Hacks
http://www.dynamicsitesolutions.com/css/filters/support-chart/
http://ajaxian.com/archives/css-browser-hacks
http://www.456bereastreet.com/archive/200411/the_underscore_hack/
For the different IE versions (usually the most important) there is a conditional IE 'if' which can handle lots of parameters: http://www.quirksmode.org/css/condcom.html