Conditional comments work in Internet Explorer and on Windows only.  For this reason, you can create special instructions to be executed by Internet Explorer only ( on Windows ). Conditional comments are for Internet Explorer 5 and higher.

The basic structure of a conditional comment is the same as an HTML comment (<!– –>). When another browser sees such comments, they will simply ignore them.

This code snippet will target Internet Explorer 6:

<!–[if IE 6]>
Special instructions for IE 6 here
<![endif]–>

This code snippet will target Internet Explorer:

<!–[if IE 7]>
According to the conditional comment this is Internet Explorer 7<br />
<![endif]–>

This will target the browser: Internet Explorer and all versions above 5:

<!–[if IE]>
According to the conditional comment this is Internet Explorer<br />
<![endif]–>

The CSS margin properties define the space around elements.

margin: top right bottom left;

The CSS property MARGIN clears the area surrounding an element. The background color of the MARGIN is transparent (no background color, at all).

Values of CSS MARGIN:
There are three possible values for the margin properties: auto, fixed, percentage.
1. Auto: The browser determines the margin.
2. Defines a fixed margin area. This area can be defined in px, pt, em, etc.
3. Defines a margin in percentage ( expressed as: % ) of the containing element

Defining margin for each side as a single statement:
margin-top: 0px;
margin-bottom: 0px;
margin-right: 0px;
margin-left: 0px;

Defining MARGIN for all sides in a single statement:
margin: top right bottom left;
margin: 1px 2px 3px 4px;

Define one value for all sides:
You can also define the margin properties using a single value, which will be applied to all sides.
margin: 1px;