>>I am sure that again I am hitting the lack of some basic understanding of CSS. So please help me understand.
>>
>>I want to include Bootstrap.css in one of the pages but BEFORE my own .CSS. So that my .CSS would take precedence.
>>
>>For example, in MY.CSS I have a class .FieldWR that set the size of the font of asp:textbox to .75em. And it works when I don't include Bootstrap.css at all. When I add the Boostrap styles in the .ASPX file, before MY.CSS the font size of the text boxes is smaller than what I want. When I look in the Chrome Developer Tools I see the following:
>>
>>

>>
>>.FieldWR { My.css: ###
>>   font-size: 0.75em;
>>   font-weight: normal:
>>}
>>
>>html {    bootstrap.min.css: ###
>>   font-size: 62.5%
>>   -webkit-tap-hightlight-color: rgba(0,0,0,0);
>>}
>>
>>

>>
>>So it looks from the above the bootstrap HTML overrides my class. Why?
>
>Could someone explain the purpose of the HTML style? Before I saw it for the first time in Bootstrap.css I didn't realize that such style exist. I thought the HTML only defines the language of the pages. But the authors of Bootstrap.css have style html { } (which causes some issues for me; or understanding).

Since the html element is the root for the entire page stlye defined for html will cascade to all child elements - looks like that in bootstrap it just defines the default font for the page...