How to make twenty eleven dropdown as horizontal

First off, do not edit the Twenty Eleven theme. It is the default WordPress theme and having access to an unedited version of the theme is vital when dealing with a range of site issues. Create a child theme for your changes. Or install a custom CSS plugin.

yes i have created a child theme as u suggested what are the css changes i need to do

You’ll now need to start unpicking the menu CSS that is being applied by the parent theme and over-writing it with new CSS in the child theme. I’d recommend using Firefox with the Firebug add-on for this kind of CSS work.
https://getfirebug.com/

Not sure what exactly you have in mind but I’d imagine that you’d want to start with:

#access ul ul {display:block;}

to make the sub-menus visible so that you can start re-styling them.

simple i like to achieve

Present Display Of twenty eleven sub menu

Menu
-menu item 1
-menu item 2
-menu item 3

Above is vertical dropdown

I need this to be

Menu
-menu item 1 -menu item 2 -menu item 3

I need it as horizontal

Have you thought how you will handle children of these sub-items?

it will not carry any child in future so no need to handle children of this submenu

I’m confused. First level children are already displayed vertically in Twenty Eleven.

Surya300, could you link to an example of what you want?

need horizontal menu not vertical (it is already displayed as u said)

I need menu like this
https://www.govisitcostarica.com/

Ah! Now I understand! I’ve released a free theme that has exactly this kind of menu:

https://quirm.net/themes/flipflop/

If you download that, you might be able to re-use the menu CSS with some tweaking.

I got this error when i tried to install the flipflop

Warning: require_once(/home/u694832405/public_html/wordpress/wp-content/themes/flipflop/library /theme-options.php) [function.require-once]: failed to open stream: No such file or directory in /home/u694832405/public_html/wordpress/wp-content/themes/flipflop/functions.php on line 99

Fatal error: require_once() [function.require]: Failed opening required ‘/home/u694832405/public_html/wordpress/wp-content/themes/flipflop/library /theme-options.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/u694832405/public_html/wordpress/wp-content/themes/flipflop/functions.php on line 99