W3C Validator Image reference list
[21793 domains; 318 unique values]

Popularity	Value	Frequency
1	xhtml10	9432
2	html401	8606
3	css	2232
4	xhtml11	1055
5	html40	815
6	wcag1A	668
7	wcag1AA	583
8	wcag1AAA	453
9	xhtml	230
10	wcag1A-small	161
11	css2	157
12	wcag1A-standard	147
13	html401.jpg	56
14	html	48
15	xhtml10.jpg	36
16	html32	36
17	css.jpg	35
18	wcag1aa	33
19	wcag1a	33
20	wcag1aaa	33
21	xhtml10-small	17
22	css-small	16
23	css1	14
24	xhtml.jpg	12
25	css.bmp	12
26	xhtml10.bmp	11
27	html401.bmp	10
28	html-401	10
29	xhtml-10	9
30	xhtml1	9
31	xhtml10-1	7
32	xhtml-11	7
33	wcag1A-blue	7
34	wcag1A.jpg	7
35	CSS	6
36	xhtml11_small	6
37	html.jpg	6
38	css21	5
39	css20	5
40	xhtml-1.0	5
41	xhtml10_small	5
42	html40.jpg	4
43	wcag1AA-blue	4
44	xhtml10.small	4
45	xhtml11.jpg	4
46	xhtml11-small	4
47	html401-small	4
48	XHTML	4