Officially we have only the outdated L3P error list:
http://www.ldraw.org/library/tracker/ref/l3pmsg/
while most of us use the output of Datheader (the following list was kindly provided by Mike Heidemann, author of the prog):
1 ERROR Embedded POV Code found. HOLD
2 ERROR '0 WRITE' found. - HOLD
3 ERROR '0 BFC CERTIFY INVERTNEXT' found. HOLD
4 ERROR '0 ROTATION' found. HOLD
5 ERROR '0 COLOR' found. HOLD
6 ERROR Incorrect use of only '0' for comments. Should be '0 //' instead.
7 ERROR Not all used colors in LDConfig.ldr. HOLD
8 ERROR Matrix all zero found. HOLD
9 ERROR Identical vertices found. HOLD
10 ERROR Colinear vertices found. HOLD
11 ERROR Bad Vertex Sequence found. HOLD
12 ERROR Concave quads found. HOLD
13 ERROR Coplanarity. HOLD
14 ERROR Incorrect color for linetype. HOLD
15 ERROR Loop in reference found. HOLD
16 ERROR Double lines found. HOLD
17 WARNING Maybe wrong color for sticker used.
18 ERROR Length of part description. HOLD
19 WARNING Maybe leading spaces in part description.
20 ERROR Keywords entry length.
21 ERROR Some keywords are also in part description. HOLD
22 ERROR Filename does not matches filetitle. HOLD
23 ERROR Author real name is not set.
24 ERROR Author user name is not set.
25 ERROR BFC is not set. HOLD
26 ERROR License is not set. HOLD
27 ERROR Part type is not set. HOLD
28 ERROR Primitives needs to have CCW winding. HOLD
29 ERROR Use of !KEYWORDS is not allowed for this part type. HOLD
30 ERROR Part description contains Tab character. HOLD
31 ERROR HELP entry length.
32 ERROR Word 'new' or 'old' is used in part description.
33 ERROR Use of (Needs work). HOLD
34 ERROR Entry for !CATEGORY.
35 ERROR Use of !CATEGORY is not allowed at for this part type.
36 ERROR High-res primitive has to start with '48\'. HOLD
37 ERROR Description for primitives should not start with '_' or '~'. HOLD
38 ERROR Filename for parts, shortcuts and primitives should not start with '48\' or 's\'. HOLD
39 ERROR Filename for subparts has to start with 's\'. HOLD
40 ERROR Description for subparts has to start with '~'. HOLD
41 ERROR Description for subparts should not start with '_' or '='.
42 ERROR Description for parts should not start with '_' or '='.
43 ERROR Description for shortcuts and/or physical_colour parts has to start with '_'. HOLD
44 ERROR Filename for shortcuts contains usually a 'c' or 'd'.
45 ERROR Extension has to be .dat HOLD
46 ERROR Special characters in description not allowed. HOLD
47 ERROR Lines do not end with <CR><LF>.
48 ERROR Author !HISTORY entry has no brackets.
49 ERROR Not scalable primitive is scaled.
50 ERROR primitive is scaled not only in Y direction.
51 ERROR First line after BFC INVERTNEXT isn't linetype 1.
52 ERROR Problem with the RGB value.
53 ERROR '~Moved to' file used.
54 ERROR Wrong BFC command found.
55 ERROR Some keywords are used twice in KEYWORDS section. HOLD
56 ERROR 'Minifig Accessory' found in part description.
57 ERROR 'Figure Accessory' found in part description.
58 WARNING 'INVERTNEXT' used although not necessary.
59 WARNING TJunktion detected.
60 ERROR Wrong brackets around username used. Only [] is allowed
61 ERROR Description for alias parts should start with '='
62 ERROR Description for Physical_Colour parts should mention the used colors
63 ERROR Only linetype 0 and 1 are allowed in Physical_Colour parts.
64 ERROR Wrong color (16 or/and 24) used for Physical_Colour part
65 ERROR Only linetype 0 and 1 are allowed in Alias parts.
66 ERROR Only one (1) linetype 1 is allowed in Alias parts.
67 ERROR Only color 16 is allowed in Alias parts.
68 ERROR Alias needs to be mentioned in the comments in the form 'Alias of partnumber'.
69 ERROR Mentioned part number in the alias comment is wrong.
70 WARNING Origin is outside the Boundingbox.
71 ERROR American English words used in part description.
72 WARNING Too much empty lines at the end of the file.
73 WARNING Mirrored studs detected.
74 WARNING Flat subfile scaled in flat direction
75 ERROR Optional line with same vertices than line found.
76 ERROR Leading or trailing zeros found.
77 ERROR Overlapping triangle found.
78 ERROR Lines with wrong number of arguments found.
79 WARNING Filename ending does not match declared LDRAW_ORG file type.
80 ERROR Moved To setnumber with Extension HOLD
81 WARNING Filename ending does not match declared LDRAW_ORG part type qualifier.
w.