As i know that conditional comments are supported only by Internet Explorer and comments are ignored by browsers.My question is that- If you put a conditional comment in a html document and open it with google chrome ,it will be displayed because it is only supported by IE not by GOOGLE chrome?
Well yeah but you really need them only for IE... as far as I know. It won't be displayed by other browser. Just try it It's like that in web development and programming - you try and try and test.
Conditional comments were the fad a few years back - nowadays, there should be absolutely no need for them, whatsoever, unless you're supporting long dead browsers. On the same note, having separate styleseets for IE and such: No. Just no.