I am trying to set background-color for div element "High Tatras" "High Tatras 2"...elements to yellow with css.

gallery li {background-color: yellow;}

jsfiddle demo http://jsfiddle.net/pragnesh/CjDDB/

But background-color yellow only applied to top and bottom part of element.

What could be problem with this code?

jquery-ui seems to have a weird multiple background css rule (lol it's not a multiple background... just the comments threw me off... it's late). Try using just the background attribute instead:

.gallery li {
    background: yellow;
}

Demo: http://jsfiddle.net/j2TtX/

The rule that is causing the background is this one:

.ui-widget-content {
    border: 1px solid #aaaaaa/*{borderColorContent}*/;
    background: #ffffff/*{bgColorContent}*/ url(images/ui-bg_flat_75_ffffff_40x100.png)/*{bgImgUrlContent}*/ 50%/*{bgContentXPos}*/ 50%/*{bgContentYPos}*/ repeat-x/*{bgContentRepeat}*/;
    color: #222222/*{fcContent}*/;
}

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