my griedview is half shown on browser's screen and even it disabled horizontal scroller on screen (browser), why ?

whenever i fill my gridview with many columns than it is half shown and disables scroller too, why ?

Maybe you applied the CSS style of overflow:hidden?

i tried overflow property and it worked ,:)
but don't you think that adding 20 columns to gridview isn't a good practice ?
am i doing right bcz it looks little ugly on page, any other way to get around ?

You should include any fields that aren't required for that view. I would only include the most important fields (maybe two or three), then make one of the fields as a hyperlink field so that when the user clicks on it you can either show a detailsview control on another page with all 20 fields.