Validation problem, please help

Hey guys, just wondering if you could help me out with this problem. For this bit of code:
19: <h4>
20: Contents
21: </h4>
22: <h5>
23:[*]
24: Elastic Design by Patrick Griffiths
25:[*]
26: The End-All Guide to Small-Screen Web-Dev by Heidi Pollock
27:[*]
28: Accesskeys: Unlocking Hidden Navigation by Stuart Robertson
29:[*]
30: Inaccessibility of Visually-Oriented Anti-Robot Tests Problems and Alternatives
31:[*]
32: 13th International World Wide Web Conference
33: </h5>

I get these problems with the validator:

Line 19, column 7: document type does not allow element "h4" here; assuming missing "li" start-tag
<h4>
^
Line 23, column 8: document type does not allow element "li" here (explain...). [*]
^
Line 25, column 8: document type does not allow element "li" here (explain...). [*]
^
Line 27, column 8: document type does not allow element "li" here (explain...). [*]
^
Line 29, column 8: document type does not allow element "li" here (explain...). [*]
^
Line 31, column 8: document type does not allow element "li" here (explain...). [*]
^
Line 34, column 7: end tag for "li" omitted, but OMITTAG NO was specified [/list]

can't have a list within a header - change the <h5> tags to <ul> (or[list=1]) tags.