Per active schema warning

[Gav]

Hi All,

Can anybody tell me why VS complains about active schema:

Code:

<div>
<asp:repeater >
<headertemplate >
<ul>
</headertemplate>
<itemtemplate >
<li>...
...
...
...
....

Complains about <ul'Per the active schema, the element 'li' cannot be
nested within 'div'.

Should I be concerned about this or should I just ignore it?

Thanks
Gav