We are in the process of nutting out the design guidelines we would like to use in our development team and got into a discussion today around how ASP.NET controls should be
Not sure about Microsoft official standards, but this is what i've done through out my development career.
I generally abbreviate the control type in front of the the name of what the control does. I keep the abbreviation lower case and the control's name CamelCase.
E.g. A texbox for username becomes tbUserName
Here is a list of standard abbreviations I use:
Abbr - Control
btn - Button
cb - CheckBox
cbl - CheckBoxList
dd - DropDownList
gv - GridView
hl - Hyperlink
img - Image
ib - ImageButton
lbl - Label
lbtn - LinkButton
lb - ListBox
lit - Literal
pnl - Panel
ph - PlaceHolder
rb - RadioButton
rbl - RadioButtonList
txt - Textbox