jQuery UI has standard icons for use with buttons, menu items, etc. These icons come in different colors for different themes. These icons are also integrated into several of the jQuery UI Widgets, such as .accordion()

To use these icons, you must link to the jQuery UI stylesheet  in your <head> ... </head> section and use a format as shown below for the element:

<link rel="stylesheet"
href="http://code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css">

<span class="ui-icon ui-icon-alert"></span>

The format shown above prepends the icon name with ui-icon- followed by one of the icon names shown below. 

ui-icon-blank
ui-icon-carat-1-n
ui-icon-carat-1-ne
ui-icon-carat-1-e
ui-icon-carat-1-se
ui-icon-carat-1-s
ui-icon-carat-1-sw
ui-icon-carat-1-w
ui-icon-carat-1-nw
ui-icon-carat-2-n-s
ui-icon-carat-2-e-w
ui-icon-triangle-1-n
ui-icon-triangle-1-ne
ui-icon-triangle-1-e
ui-icon-triangle-1-se
ui-icon-triangle-1-s
ui-icon-triangle-1-sw
ui-icon-triangle-1-w
ui-icon-triangle-1-nw
ui-icon-triangle-2-n-s
ui-icon-triangle-2-e-w
ui-icon-arrow-1-n
ui-icon-arrow-1-ne
ui-icon-arrow-1-e
ui-icon-arrow-1-se
ui-icon-arrow-1-s
ui-icon-arrow-1-sw
ui-icon-arrow-1-w
ui-icon-arrow-1-nw
ui-icon-arrow-2-n-s
ui-icon-arrow-2-ne-sw
ui-icon-arrow-2-e-w
ui-icon-arrow-2-se-nw
ui-icon-arrowstop-1-n
ui-icon-arrowstop-1-e
ui-icon-arrowstop-1-s
ui-icon-arrowstop-1-w
ui-icon-arrowthick-1-n
ui-icon-arrowthick-1-ne
ui-icon-arrowthick-1-e
ui-icon-arrowthick-1-se
ui-icon-arrowthick-1-s
ui-icon-arrowthick-1-sw
ui-icon-arrowthick-1-w
ui-icon-arrowthick-1-nw
ui-icon-arrowthick-2-n-s
ui-icon-arrowthick-2-ne-sw
ui-icon-arrowthick-2-e-w
ui-icon-arrowthick-2-se-nw
ui-icon-arrowthickstop-1-n
ui-icon-arrowthickstop-1-e
ui-icon-arrowthickstop-1-s
ui-icon-arrowthickstop-1-w
ui-icon-arrowreturnthick-1-w
ui-icon-arrowreturnthick-1-n
ui-icon-arrowreturnthick-1-e
ui-icon-arrowreturnthick-1-s
ui-icon-arrowreturn-1-w
ui-icon-arrowreturn-1-n
ui-icon-arrowreturn-1-e
ui-icon-arrowreturn-1-s
ui-icon-arrowrefresh-1-w
ui-icon-arrowrefresh-1-n
ui-icon-arrowrefresh-1-e
ui-icon-arrowrefresh-1-s
ui-icon-arrow-4
ui-icon-arrow-4-diag
ui-icon-extlink
ui-icon-newwin
ui-icon-refresh
ui-icon-shuffle
ui-icon-transfer-e-w
ui-icon-transferthick-e-w
ui-icon-folder-collapsed
ui-icon-folder-open
ui-icon-document
ui-icon-document-b
ui-icon-note
ui-icon-mail-closed
ui-icon-mail-open
ui-icon-suitcase
ui-icon-comment
ui-icon-person
ui-icon-print
ui-icon-trash
ui-icon-locked
ui-icon-unlocked
ui-icon-bookmark
ui-icon-tag
ui-icon-home
ui-icon-flag
ui-icon-calculator
ui-icon-cart
ui-icon-pencil
ui-icon-clock
ui-icon-disk
ui-icon-calendar
ui-icon-zoomin
ui-icon-zoomout
ui-icon-search
ui-icon-wrench
ui-icon-gear
ui-icon-heart
ui-icon-star
ui-icon-link
ui-icon-cancel
ui-icon-plus
ui-icon-plusthick
ui-icon-minus
ui-icon-minusthick
ui-icon-close
ui-icon-closethick
ui-icon-key
ui-icon-lightbulb
ui-icon-scissors
ui-icon-clipboard
ui-icon-copy
ui-icon-contact
ui-icon-image
ui-icon-video
ui-icon-script
ui-icon-alert
ui-icon-info
ui-icon-notice
ui-icon-help
ui-icon-check
ui-icon-bullet
ui-icon-radio-off
ui-icon-radio-on
ui-icon-pin-w
ui-icon-pin-s
ui-icon-play
ui-icon-pause
ui-icon-seek-next
ui-icon-seek-prev
ui-icon-seek-end
ui-icon-seek-first
ui-icon-stop
ui-icon-eject
ui-icon-volume-off
ui-icon-volume-on
ui-icon-power
ui-icon-signal-diag
ui-icon-signal
ui-icon-battery-0
ui-icon-battery-1
ui-icon-battery-2
ui-icon-battery-3
ui-icon-circle-plus
ui-icon-circle-minus
ui-icon-circle-close
ui-icon-circle-triangle-e
ui-icon-circle-triangle-s
ui-icon-circle-triangle-w
ui-icon-circle-triangle-n
ui-icon-circle-arrow-e
ui-icon-circle-arrow-s
ui-icon-circle-arrow-w
ui-icon-circle-arrow-n
ui-icon-circle-zoomin
ui-icon-circle-zoomout
ui-icon-circle-check
ui-icon-circlesmall-plus
ui-icon-circlesmall-minus
ui-icon-circlesmall-close
ui-icon-squaresmall-plus
ui-icon-squaresmall-minus
ui-icon-squaresmall-close
ui-icon-grip-dotted-vertical
ui-icon-grip-dotted-horizontal
ui-icon-grip-solid-vertical
ui-icon-grip-solid-horizontal
ui-icon-gripsmall-diagonal-se
ui-icon-grip-diagonal-se