To add some more details to EkoJr's answer, as of Jquery UI v1.11.4 if you add the whole JQuery UI CSS stylesheet, it might break the default Wordpress Theme styling.
So, you could only add the CSS classes corresponding to the slider component. Here are the classes I used (note : these are built for the ui-darkness theme) :
.ui-state-default,
.ui-widget-content .ui-state-default,
.ui-widget-header .ui-state-default {
border: 1px solid #666666;
/* this image is from the ui-darkness theme, use the one you'd like */
background: #555555 url("img/jquery-ui/ui-bg_glass_20_555555_1x400.png") 50% 50% repeat-x;
font-weight: bold;
color: #eeeeee;
}
.ui-slider-horizontal .ui-slider-handle {
top: -.3em;
margin-left: -.6em;
}
.ui-slider .ui-slider-handle {
position: absolute;
z-index: 2;
width: 1.2em;
height: 1.2em;
cursor: default;
-ms-touch-action: none;
touch-action: none;
}
.ui-corner-all,
.ui-corner-bottom,
.ui-corner-right,
.ui-corner-br {
border-bottom-right-radius: 6px;
}
.ui-corner-all,
.ui-corner-bottom,
.ui-corner-left,
.ui-corner-bl {
border-bottom-left-radius: 6px;
}
.ui-corner-all,
.ui-corner-top,
.ui-corner-right,
.ui-corner-tr {
border-top-right-radius: 6px;
}
.ui-corner-all,
.ui-corner-top,
.ui-corner-left,
.ui-corner-tl {
border-top-left-radius: 6px;
}
.ui-corner-all,
.ui-corner-bottom,
.ui-corner-right,
.ui-corner-br {
border-bottom-right-radius: 6px;
}
.ui-corner-all,
.ui-corner-bottom,
.ui-corner-left,
.ui-corner-bl {
border-bottom-left-radius: 6px;
}
.ui-corner-all,
.ui-corner-top,
.ui-corner-right,
.ui-corner-tr {
border-top-right-radius: 6px;
}
.ui-corner-all,
.ui-corner-top,
.ui-corner-left,
.ui-corner-tl {
border-top-left-radius: 6px;
}
.ui-widget-content {
border: 1px solid #666666;
/* this image is from the ui-darkness theme, use the one you'd like */
background: #000000 url("img/jquery-ui/ui-bg_inset-soft_25_000000_1x100.png") 50% bottom repeat-x;
color: #ffffff;
}
.ui-widget {
font-family: Segoe UI,Arial,sans-serif;
font-size: 1.1em;
}
.ui-slider-horizontal {
height: .8em;
}
.ui-slider {
position: relative;
text-align: left;
}
Also, please note that you can prefix those classes with your container ID. For exemple, if your slider has the ID 'slider', use :
#slider .ui-state-default,
#slider .ui-widget-content .ui-state-default,
#slider .ui-widget-header .ui-state-default {
border: 1px solid #666666;
/* this image is from the ui-darkness theme, use the one you'd like */
background: #555555 url("img/jquery-ui/ui-bg_glass_20_555555_1x400.png") 50% 50% repeat-x;
font-weight: bold;
color: #eeeeee;
}
....ETC