<style type="text/css">
        .searchwordsblock
        {
            left: 0%;
            width: 100%;
            min-height:80px;
            position: relative;
            background-color: #CCFFee;                     
        }
        .left-column
        {
            width:16%;
            background:red;
            float:left;
            position:relative;                     
        }
        .right-column
        {        
            width:84%;
            background:green;
            float:right;
            position:relative;
            resize: none;
        }

 <div ID="searchwordsblock" class ="searchwordsblock">
    
      <span class="left-column" "seek-word-list">
      <h2> Search words </h2>
      </span>
        
      <div class="right-column">
        <asp:TextBox ID="SeekWordsList" runat="server" 
            title="Enter the list of words delimited with spaces that you want to find in the data source" 
            Wrap="True" 
            height="75"
            resize= "none"          
            overflow="auto"          
            position="relative" TextMode="MultiLine">
         </asp:TextBox>
      </div>
    </div>    <!-- class searchwordblock-->