How to apply css to rowstyle of gridview?

There are several way to do that

1- designer page - itemstyle

you can make difference between even and odd rows if you want

<itemstyle cssclass="lnknew" />
<alternatingitemstyle cssclass="lnknew" />

2- code behind - itemstyle usually in a init() method on pageload

grvShowhistory.HeaderStyle.CssClass = "lnknew";
grvShowhistory.RowStyle.CssClass = "lnknew";

3- code behind - itemdatabound (make sure to have an itemdataboud method in the designer page

protected void dgv_ItemDataBound(object sender, DataGridItemEventArgs e)
{
    switch (e.Item.ItemType)
    {
        case ListItemType.Item:
        case ListItemType.AlternatingItem:
            if(yourCondition)
            {
                e.Item.CssClass += "lnknew";
            }
            break;
    }
}

4- code behind - free code

foreach (GridViewRow row in grvShowhistory.Rows)
{
    row.CssClass = "lnknew";
}

this will be

<table>
<tr class="lnknew">
<td>
</td>
...

if you need to style the TD element you have to do match the element in the row

bye