In advance settings of Question contain one field CSS Class(es) which is used to add extra css to question but i didn't get how to add the css classes where we should declare the class and how to include this classes. can you tell me about this ?
Thank you...

Here is an example where it is used and explained
www.limesurvey.org/forum/design-issues/1...ions-in-2-x-2-matrix

i get some hint from this example but i didn't understand where should i write this class so that it will apply css for that part of question...

Hi, shhivani,
But it's said explicitly in Tony's answer :

In the advanced question settings, you can define a CSS class for the questions. Let's say "my-slider-question" for the sliders and "my-text-question" for the long-texts.

Then in template.css, you can apply styles to the questions something like this. It should place them side-by-side.

.my-slider-question {
float: left;
width: 32%;
margin-right: 2%;
clear: left;
}

.my-text-question {
float: left;
width: 65%;
}

Otherwise read about template editor, here:
www.limesurvey.org/manual/The_template_editor

Best regards
Joffm

thank you...