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UI
Pixel
Fugue Icons
compile, warning
Black
16x16
Desktop apps
3D
Alert, warning
Orange
48x48
Mixed
Iconza
warning
SeaGreen
32x32
Computer & hardware
Human o2
warning, gtk, Print
WhiteSmoke
128x128
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Mini icons 2
Lavender
10x10
Gnome icons
warning, gtk, Dialog
SandyBrown
C9d
warning, Info
LightSkyBlue
24x24
Splashyfish
osx, warning, Application
windows, Application, warning
warning, Box, weight
Khaki
warning, A4, document
Snow
warning, document, Letter
warning, documents
Silver
Error, Attention, exclamation
Red
triangle, Attention, warning
notice, Alert, triangle
Shopping & e-commerce
Smooth
Woothemes Ultimate Icon Set
warning, document
warning, stop
Tomato
Tango
warning, Dialog
Family & home
Cartoon
Kids
Critical, Attention, Error
Led Icons
stop, Alert, warning
Chocolate
Crystal Project
messagebox, warning
256x256
Photography & graphic design
Dark Glass
Call, Alert, Chat