Custom Master Pages in WSS3.0 / SharePoint 2007 DOC TYPE

I have a custom master page that I use in WSS3.0 (SharePoint 2007) and I am using a HTML 'DOC TYPE' which I am declaring at the top of the master page. The site all works very well with my master page apart from some of SharePoint controls which are acting a little funny, namely the People Picker for a People and Group field.

If I remove the DOC TYPE declaration then the People Picker and other controls work perfectly and behave as they should but it sends some of my customisations/layout all over.

Before I spend a lot of time reviewing fixing the issues I get to my design without having the DOC TYPE declared, does anyone know if there is a certain DOC TYPE that is compatible with WSS3.0 / SharePoint 2007 and all of its features (i.e. People 开发者_开发知识库Picker Fields)?

Any help would be greatly appreciated...

Cheers

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Heather Solomon (a super expert at SharePoint branding) has some sample SP2007 minimal master pages here: http://www.heathersolomon.com/blog/articles/BaseMasterPages.aspx and for them she uses DTD HTML 4.01 Transitional.