Select Unicode code range and test for visible characters?
Don't worry if you can't see everything
This test goes from the very simple to the very advanced.

Any modern browser should be able to handle all of these code points,
but if your operating system is not setup properly the browser will display
the default character, usually a square or a question mark.

For any code block, If you see squares or question marke or
some other default character, it means that
1) Your computer is not enabled for that language yet
2) You do not have the fonts for that code block, or they are not set properly
3) Sometimes you will see squares at the end of a code block because
Unicode has not defined those code points.

Unicode alocates the following code points Unicode Character Sets and their encodings: (U+0000" to U+10FFFF)

The following two .pdf files show graphical representations of all the Unicode code points
so you will know what you should be seeing.

PDF Unicode 4.0 CodeCharts
PDF Unicode 5.2 Alternates CJK CodeCharts

The code points are in planes as follows
Unicode BMP (Basic Multilingual Plane) Plane 0 (U+0000 to U+", "FFFF)
Unicode SMP (Supplementary Multilingual Plane) Plane 1 (U+10000 to U+1FFFF)
Unicode SIP (Supplementary Ideographic Plane) Plane 3 (U+20000 to U+2FFFF)
Unicode TIP (Tertiary Ideographic Plane) Plane 3 (U+30000 to U+3FFFF)

To properly view my web site you should be enabled for the first 3 levels of Chinese characters

CJK Unified Ideograms Unified Ideographs: (U+4E00 to U+9FFF)

This is enough for everyday Chinese, but to make full use of my web site you will need Extenstion A and Extension B

CJK Ideographs Extension A: (U+3400 to U+4DBF)

This is the first extension of rare characters. You will need this to mske full use of my site.

CJK Ideographs Extension B: (U+20000 to U+2A6DF)

This is the second extension of rare characters. You will also need this.

CJK Ideographs Extension C: (U+2A700 to U+2B73F)

CJK Ideographs Extension D: (U+2B740 to U+2B81F)

Hangul Syllables (U+AC00 to U+D7AF)

Code blocks defined in Unicode 6.0

BMP Latin 1: (U+0000 to U+00FF)
extended ASCII. ASCII is only 7 bits (U+0000 to U+007F)
CJK Compatability Ideographs Supplement: (U+2F800 to U+2FA1F)
CJK Radicals Supplement: (U+2E80 to U+2EFF)
Kangxi Radicals: (U+2F00 to U+2FDF)
Ideographic Description Characters: (U+2FF0 to U+2FFF)
CJK Symbols and Punctuation: (U+3000 to U+303F)
Hiragana: (U+3040 to U+309F)
Katakana: (U+30A0 to U+30FF)
Bopomofo: (U+3100 to U+312F)
Hangul Compatibility Jamo: (U+3130 to U+318F)
Kanbun: (U+3190 to U+319F)
Bopomofo Extended: (U+31A0 to U+31BF)
CJK Strokes: (U+31C0 to U+31EF)
Katakana Phonetic Extensions: (U+31F0 to U+31FF)
Enclosed CJK Letters and Months: (U+3200 to U+32FF)
CJK Compatibility: (U+3300 to U+33FF)
CJK Unified Ideographs Extension A: (U+3400 to U+4DBF)
Yijing Hexagram Symbols: (U+4DC0 to U+4DFF)
CJK Compatibility Ideographs: (U+F900 to U+FAFF)
CJK Compatibility Forms: (U+FE30 to U+FE4F)
Half width and Full width Forms: (U+FF00 to U+FFEF)}
C0 Controls and Basic Latin (Basic latin) (0000 to U+007F)
C1 Controls and Latin-1 Supplement (0080 to U+00FF)
Latin Extended-A (0100 to U+017F)
Latin Extended-B (0180 to U+024F)
IPA Extensions (0250 to U+02AF)
Spacing Modifier Letters (02B0 to U+02FF)
Combining Diacritical Marks (0300 to U+036F)
Greek and Coptic (0370 to U+03FF)
Cyrillic (U+0400 to U+04FF)
Cyrillic Supplement (U+0500 to U+052F)
Armenian (U+0530 to U+058F)
Hebrew (U+0590 to U+05FF)
Arabic (U+0600 to U+06FF)
Syriac (U+0700 to U+074F)
Arabic Supplement (U+0750 to U+077F)
Thaana (U+0780 to U+07BF)
NKo (U+07C0 to U+07FF)
Samaritan (U+0800 to U+083F)
Mandaic (U+0840 to U+085F)
Devanagari (U+0900 to U+097F)
Bengali (U+0980 to U+09FF)
Gurmukhi (U+0A00 to U+0A7F)
Gujarati (U+0A80 to U+0AFF)
Oriya (U+0B00 to U+0B7F)
Tamil (U+0B80 to U+0BFF)
Telugu (U+0C00 to U+0C7F)
Kannada (U+0C80 to U+0CFF)
Malayalam (U+0D00 to U+0D7F)
Sinhala (U+0D80 to U+0DFF)
Thai (U+0E00 to U+0E7F)
Lao (U+0E80 to U+0EFF)
Tibetan (U+0F00 to U+0FFF)
Myanmar (U+1000 to U+109F)
Georgian (U+10A0 to U+10FF)
Hangul Jamo (U+1100 to U+11FF)
Ethiopic (U+1200 to U+137F)
Ethiopic Supplement (U+1380 to U+139F)
Cherokee (U+13A0 to U+13FF)
Unified Canadian Aboriginal Syllabics (U+1400 to U+167F)
Ogham (U+1680 to U+169F)
Runic (U+16A0 to U+16FF)
Tagalog (U+1700 to U+171F)
Hanunoo (U+1720 to U+173F)
Buhid (U+1740 to U+175F)
Tagbanwa (U+1760 to U+177F)
Khmer (U+1780 to U+17FF)
Mongolian (U+1800 to U+18AF)
Unified Canadian Aboriginal Syllabics Extended (U+18B0 to U+18FF)
Limbu (U+1900 to U+194F)
Tai Le (U+1950 to U+197F)
Tai Lue (U+1980 to U+19DF)
Khmer Symbols (U+19E0 to U+19FF)
Buginese (U+1A00 to U+1A1F)
Tai Tham (U+1A20 to U+1AAF)
Balinese (U+1B00 to U+1B7F)
Sundanese (U+1B80 to U+1BBF)
Batak (U+1BC0 to U+1BFF)
Lepcha (U+1C00 to U+1C4F)
Ol Chiki (U+1C50 to U+1C7F)
Vedic Extensions (U+1CD0 to U+1CFF)
Phonetic Extensions (U+1D0 to U+1D7F)
Phonetic Extensions Supplement (U+1D80 to U+1DBF)
Combining Diacritical Marks Supplement (U+1DC0 to U+1DFF)
Latin extended additional (U+1E00 to U+1EFF)
Greek Extended (U+1F00 to U+1FFF)
General Punctuation (U+2000 to U+206F)
Superscripts and Subscripts (U+2070 to U+209F)
Currency Symbols (U+20A0 to U+20CF)
Combining Diacritical Marks for Symbols (U+20D0 to U+20FF)
Letterlike Symbols (U+2100 to U+214F)
Number Forms (U+2150 to U+218F)
Arrows (U+2190 to U+21FF)
Mathematical Operators (U+2200 to U+22FF)
Miscellaneous Technical (U+2300 to U+23FF)
Control Pictures (U+2400 to U+243F)
Optical Character Recognition (U+2440 to U+245F)
Enclosed Alphanumerics (U+2460 to U+24FF)
Box Drawing (U+2500 to U+257F)
Block Elements (U+2580 to U+259F)
Geometric Shapes (U+25A0 to U+25FF)
Miscellaneous Symbols (U+2600 to U+26FF)
Dingbats (U+2700 to U+27BF)
Miscellaneous Mathematical Symbols-A (U+27C0 to U+27EF)
Supplemental Arrows-A (U+27F0 to U+27FF)
Braille Patterns (U+2800 to U+28FF)
Supplemental Arrows-B (U+2900 to U+297F)
Miscellaneous Mathematical Symbols-B (U+2980 to U+29FF)
Supplemental Mathematical Operators (U+2A00 to U+2AFF)
Miscellaneous Symbols and Arrows (U+2B00 to U+2BFF)
Glagolitic (U+2C00 to U+2C5F)
Latin Extended-C (U+2C60 to U+2C7F)
Coptic (U+2C80 to U+2CFF)
Georgian Supplement (U+2D00 to U+2D2F)
Tifinagh (U+2D30 to U+2D7F)
Ethiopic Extended (U+2D80 to U+2DDF)
Cyrillic Extended-A (U+2DE0 to U+2DFF)
Supplemental Punctuation (U+2E00 to U+2E7F)
Yi Syllables (U+A000 to U+A48F)
Yi Radicals (U+A490 to U+A4CF)
Lisu (U+A4D0 to U+A4FF)
Vai (U+A500 to U+A63F)
Cyrillic Extended-B (U+A640 to U+A69F)
Bamum (U+A6A0 to U+A6FF)
Modifier Tone Letters (U+A700 to U+A71F)
Latin Extended-D (U+A720 to U+A7FF)
Syloti Nagri (U+A800 to U+A82F)
Common Indic Number Forms (U+A830 to U+A83F)
Phags-pa (U+A840 to U+A87F)
Saurashtra (U+A880 to U+A8DF)
Devanagari Extended (U+A8E0 to U+A8FF)
Kayah Li (U+A900 to U+A92F)
Rejang (U+A930 to U+A95F)
Hangul Jamo Extended-A (U+A960 to U+A97F)
Javanese (U+A980 to U+A9DF)
Cham (U+AA00 to U+AA5F)
Myanmar Extended-A (U+AA60 to U+AA7F)
Tai Viet (U+AA80 to U+AADF)
Ethiopic Extended-A (U+AB00 to U+AB2F)
Meetei Mayek (U+ABC0 to U+ABFF)
Hangul Syllables (U+AC00 to U+D7AF)
Hangul Jamo Extended-B (U+D7B0 to U+D7FF)
High Surrogates (U+D800 to U+DB7F)
High Private Use Surrogates (U+DB80 to U+DBFF)
Low Surrogates (U+DC00 to U+DFFF)
Private Use Area (U+E000 to U+F8FF)
Alphabetic Presentation Forms (U+FB00 to U+FB4F)
Arabic Presentation Forms-A (U+FB50 to U+FDFF)
Variation Selectors (U+FE00 to U+FE0F)
Vertical Forms (U+FE10 to U+FE1F)
Combining Half Marks (U+FE20 to U+FE2F)
CJK Compatibility Forms (U+FE30 to U+FE4F)
Small Form Variants (U+FE50 to U+FE6F)
Arabic Presentation Forms-B (U+FE70 to U+FEFF)
Halfwidth and Fullwidth Forms (U+FF00 to U+FFEF)
Specials (U+FFF0 to U+FFFF)
Linear B Syllabary (U+10000 to U+1007F)
Linear B Ideograms (U+10080 to U+100FF)
Aegean Numbers (U+10100 to U+1013F)
Ancient Greek Numbers (U+10140 to U+1018F)
Ancient Symbols (U+10190 to U+101CF)
Phaistos Disc (U+101D0 to U+101FF)
Lycian (U+10280 to U+1029F)
Carian (U+102A0 to U+102DF)
Old Italic (U+10300 to U+1032F)
Gothic (U+10330 to U+1034F)
Ugaritic (U+10380 to U+1039F)
Old Persian (U+103A0 to U+103DF)
Deseret (U+10400 to U+1044F)
Shavian (U+10450 to U+1047F)
Osmanya (U+10480 to U+104AF)
Cypriot Syllabary (U+10800 to U+1083F)
Imperial Aramaic (U+10840 to U+1085F)
Phoenician (U+10900 to U+1091F)
Lydian (U+10920 to U+1093F)
Kharoshthi (U+10A00 to U+10A5F)
Old South Arabian (U+10A60 to U+10A7F)
Avestan (U+10B00 to U+10B3F)
Inscriptional Parthian (U+10B40 to U+10B5F)
Inscriptional Pahlavi (U+10B60 to U+10B7F)
Old Turkic (U+10C00 to U+10C4F)
Rumi Numeral Symbols (U+10E60 to U+10E7F)
Brahmi (U+11000 to U+1107F)
Kaithi (U+11080 to U+110CF)
Cuneiform (U+12000 to U+123FF)
Cuneiform Numbers and Punctuation (U+12400 to U+1247F)
Egyptian Hieroglyphs (U+13000 to U+1342F)
Bamum Supplement (U+16800 to U+16A3F)
Kana Supplement (U+1B000 to U+1B0FF)
Byzantine Musical Symbols (U+1D000 to U+1D0FF)
Musical Symbols (U+1D100 to U+1D1FF)
Ancient Greek Musical Notation (U+1D200 to U+1D24F)
Tai Xuan Jing Symbols (U+1D300 to U+1D35F)
Counting Rod Numerals (U+1D360 to U+1D37F)
Mathematical Alphanumeric Symbols (U+1D400 to U+1D7FF)
Mahjong Tiles (U+1F000 to U+1F02F)
Domino Tiles (U+1F030 to U+1F09F)
Playing Cards (U+1F0A0 to U+1F0FF)
Enclosed Alphanumeric Supplement (U+1F100 to U+1F1FF)
Enclosed Ideographic Supplement (U+1F200 to U+1F2FF)
Miscellaneous Symbols And Pictographs (U+1F300 to U+1F5FF)
Emoticons (U+1F600 to U+1F64F)
Transport And Map Symbols (U+1F680 to U+1F6FF)
Alchemical Symbols (U+1F700 to U+1F77F)