Problem with visualization SPmenuField in SPGridView

Question

I have created SPGridView and added one SPMenuField as the first column and some BoundFields. Then I added MenuTemplate to the first column. But there are rectangles with white color border (look at the picture). I want to hide them. How can I do it ?

Here is the code I use:

   SPMenuField colMenu = new SPMenuField();
   colMenu.HeaderText = "Title";
   colMenu.TextFields = "Title";
   colMenu.MenuTemplateId = "TitleListMenu";
   colMenu.NavigateUrlFields = "WebId, ListId, ID";
   colMenu.NavigateUrlFormat = "default.aspx?WebID={0}&ListID={1}&ListItemID={2}";
   colMenu.TokenNameAndValueFields = "Param1=ID";
   colMenu.SortExpression = "Title";

   MenuTemplate typeListMenu = new MenuTemplate();
   typeListMenu.ID = "TitleListMenu";

   // ... //

   Controls.Add(typeListMenu);
   customGridView.Columns.Add(colMenu);

Answer 1

Use the build-in webdeveloper tool in the browser (F12) and inspect the element.
I'm pretty sure it's just border around the contextmenu div.

Add the below to your CSS file and brand it. Beware that this will change it for all contextmenus on your site using your CSS file, so you might want to narrow it down to your custom list.

Over all:

.s4-ctx{ }

Narrowed:

#TitleListMenu .s4-ctx{ }