Kumar

Here is the solution that i have found . Go to your file manager and find meta-boxes.php in the location /wp-admin/includes/ inside your wordpress installed directory.You will find these functions function post_format_meta_box( $post, $box ) and function post_categories_meta_box( $post, $box ) . You can either comment these functions or you can override these functions. However, it may affect future WordPress Upgrades.

You can do this with your ftp file manager or else contact the hosting provider if you are not sure what to do.

In the style.css ,If you are using twenty eleven theme you will find a comment statement Header .
#site-title {
margin-right: 270px;
padding: 3.65625em 0 0;
}
#site-title a {
color: #111;
font:30px “Helvetica Neue”, Helvetica, Arial, sans-serif;

font-weight: bold;
line-height: 36px;
text-decoration: none;
}
The code which is in bold is the place you have to insert your required font names. Use only installed fonts.

You can change it in the style.css .