Here is a way of detecting search engine (Google, live…) crawlers,spiders etc..

[code:c#]
            System.Web.HttpBrowserCapabilities clientBrowserCaps = Request.Browser;
            if (((System.Web.Configuration.HttpCapabilitiesBase)clientBrowserCaps).Crawler)
            {
                Response.Write ( "Browser is a search engine.");
            }
            else
            {
               Response.Write ("Browser is not a search engine.");
            } 

//Here is another approach..

            if (Request.ServerVariables["HTTP_USER_AGENT"].Contains("Googlebot"))
            {
                //log Google bot visit
            }
            else if (Request.ServerVariables["HTTP_USER_AGENT"].Contains("msnbot"))
            {
                //log MSN bot visit
            }
            else if (Request.ServerVariables["HTTP_USER_AGENT"].Contains("Yahoo"))
            {
                //log yahoo bot visit
            }
            else
            {
                //similarly you can check for other search engines
            }

[/code]

Web Site Project is deployed with source code to the server and all compilation takes place at runtime.

Web Application Projects, the code behind classes are compiled to dll. That dll is deployed and at runtime, the compiled code in the dll and the markup is combined to create a class which is used by the server to render output.

Update:

Good post by anthony on this

post by Stephen on this topic

Here is a small code to remove spaces from textbox's text in onblur event.

<asp:TextBox ID="TextBox2" runat="server" onblur="javascript:value=value.replace(/\s/g,'');"></asp:TextBox>

To remove HTML tags..

<asp:textbox id="TextBox2" runat="server" onblur="this.value = this.value.replace(/<\/?[^>]+>/gi, '');">
</asp:textbox>

Please let me know, if you have any issues.

Here is a way of changing back ground color for Textbox on validation failure. The key here is using Page_ClientValidate function in javascript.

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="Please enter a value"
    ControlToValidate="TextBox1"></asp:RequiredFieldValidator>
<asp:Button ID="Button1" runat="server" Text="Button" OnClientClick="btnClick();"
    OnClick="Button1_Click1" />

<script type="text/javascript"> 

    function btnClick() 
    { 
        if (!Page_ClientValidate()) 
        { 
            document.getElementById("TextBox1").style.backgroundColor="red"; 
        } 
    } 

    function ClearBackGround() 
    { 
        document.getElementById("TextBox1").style.backgroundColor=""; 
    } 

</script>

In Code behind

TextBox1.Attributes.Add("onkeypress", "ClearBackGround()");

Regular expression for validating time part: (([0-1][0-9])|([2][0-3])):([0-5][0-9])

if a column in DB table is a datetime and you need to compare TIME only (without DATE) , there is no built in function for that.

Here is small Query to perform that task. The key is converting both to same Date

@time1 datetime  
@time2 datetime 
select @time1 = '1900-01-01 07:30:00.000',
 @time2 = '1899-12-30 07:30:00.000' 
-- This convert both @time1 & @time2 into same date (1900-01-01) such that you can compare the time. 
-- Note : Resuls is a datetime
select tm1 = dateadd(day, datediff(day, 0, @time1) * -1, @time1),  
-- This uses convert function + substring to extract the time. 
-- Note : Result will be a varchar
tm2 = dateadd(day, datediff(day, 0, @time2) * -1, @time2)
select tm1 = substring(convert(varchar(25), @time1, 121), 12, 12), tm2 = substring(convert(varchar(25), @time2, 121), 12, 12) 
---Comapre tm1 & tm2 

Thanks to tip from "khtan" of SqlTeam

The browser back button cannot be disabled as the browser security will not allow this. If you want user to stay on the same page, even if user presses back button, try this java script..

<script language="JavaScript">

javascript:window.history.forward(1);

</script>

What if the JavaScript is disabled by the client, then this code doesn't work. And also it works great in IE, but not in other browsers. So I do not highly recommend using this.

Here is another solution for back button problem..

Add this code to Page_load

Response.Cache.SetCacheability(HttpCacheability.NoCache);

Response.Cache.SetExpires(DateTime.Now); 

The above code will disable page cache. Since the page is not being cached on the browser, the page will be reloaded when the user hits the back button.

HTTP(web page) is stateless, so we cannot know whether the Session has really expired without sending a page request back to the server. If you want to redirect the page immediately(with out any user action) after session expires consider this approach.

Response.AppendHeader("Refresh",Convert.ToString((Session.Timeout * 60)+ 10)+";URL=Login.aspx");

Add this line of code to page_Load.

Sometimes we have to capture page close event or navigation event to alert users. For example, Alerting user for navigating away from input page without saving it. Check this java script code..

window.onbeforeunload= function(){
if((window.event.clientX<0) || (window.event.clientY<0))
    {
      event.returnValue = "Are you sure you want to navigate away from this page? You haven't saved this form.";
    }
};

This code works only in Ie6/7. And also keep in mind, we can never catch the browser close event for 100%. For example, what if the user kills the browser process or shut down OS.