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Asp.net button avoid pageload onclick

I have one asp button I want avoid pageload on button click
Plz someone help
Even JavaScript method will be ok for me

The framework fundamentally does not work that way. If you stay true to the framework, you can wrap your button in an update panel. That will remove the visible postback, but that will still fire the postback and perform the page load and click event.
In essence the update panel will dump your entire page into memory, then reload only the differences, simulating an ajax request.
The link submitted only allows the button to perform a JavaScript function, which would still need to Ajax to the backend.
<asp:UpdatePanel ID="upSample" runat="server" ...>
<ContentTemplate>
<asp:Button id="btnSample" runat="server" ... />
</ContentTemplate>
</asp:UpdatePanel>
Otherwise you should not use a server side event at all, simply do traditional html <input type="button" click="btnSample_Click()" /> that is actually doing Ajax directly to the server side.

How to stop refreshing the page

Is there any chance to stop the page to refresh on every pressed control?
For example: I change the selection of a DropDownList and the page refreshes. It just feels weird.
I do it with a form tag runat="server"

Try using UpdatePanel and here you can find how to use the update Panel sample code.
easiest way to stop refeshing
Regarding PostBack:
PostBack is the name given to the process of submitting an ASP.NET page to the server for processing. PostBack is done if certain credentials of the page are to be checked against some sources (such as verification of username and password using database). This is something that a client machine is not able to accomplish and thus these details have to be 'posted back' to the server.
What is AutoPostBack Property in ASP.NET:
If we create a web Page, which consists of one or more Web Controls that are configured to use AutoPostBack (Every Web controls will have their own AutoPostBack property), the ASP.NET adds a special JavaScipt function to the rendered HTML Page. This function is named _doPostBack() . When Called, it triggers a PostBack, sending data back to the web Server.
Understanding PostBack
Try putting update panel for dropdown with triggers
<asp:UpdatePanel ID="upSetSession" runat="server">
<ContentTemplate>
<asp:DropDownList ID="ddlMyList" runat="server"
onselectedindexchanged="ddlMyList_SelectedIndexChanged"
AutoPostBack="true">
<asp:ListItem>Select One</asp:ListItem>
<asp:ListItem>Maybe</asp:ListItem>
<asp:ListItem>Yes</asp:ListItem>
</asp:DropDownList>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="ddlMyList"
EventName="SelectedIndexChanged" />
</Triggers>
</asp:UpdatePanel>

From asp.net:
Perhaps the most visible feature of the ASP.NET AJAX Extensions is the ability to do a partial or incremental page updates without doing a full postback to the server, with no code changes and minimal markup changes. The advantages are extensive – the state of your multimedia (such as Adobe Flash or Windows Media) is unchanged, bandwidth costs are reduced, and the client does not experience the flicker usually associated with a postback.
Integrate partial rendering into your project. Have a look at this link.
Also OnClientClick="return false;" may help but adding OnClientClick="return false;" on every button, is not a good idea. Partial rendering and AJAX is the better solution.

Using multiple forms, submit buttons on an ASP.NET web forms page

I have 3 different submit buttons(Log In, Search, Insert) in the same page and what I want is to find the best way to have this 3 buttons doing a different things when I press them, or I press enter while I am about to press them.
As you can see from my photo, when I press Log In the Insert is pressed too because I have a global form in my Master Page.
I tried to use different forms, but i can't because I need them to have runat="server", which is not possible for a page to have.
I use asp Texboxes:
<asp:TextBox class="text-input" ID="txtLoginEmail" runat="server"
Height="15px" Width="130px"></asp:TextBox>
and asp Buttons:
<asp:Button class="submit google-button" ID="btnLogin" onclick="btnLogin_Click"
runat="server" Text="Log in" />
except my Search button which is linkButton:
<asp:LinkButton ID="searchLink" runat="server" onclick="searchLink_Click">Search</asp:LinkButton>

You may use Validation Groups to cause only required text boxes validation on specific button click. And then in event handler to concrete button you may execute specific logic.

How to show a html button for asp:button click

I have an asp.net web page with asp:button control. I need to show two (normal) HTML buttons for the click event of the asp:button control.
My requirement is when the page load for the first time there will be only asp:button there visible. After I click on that asp:button other two HTML buttons should be visible. But they should be visible for all the other postbacks. I mean if there would be any post backs, that HTML buttons should be visible constantly. How could I do that? Please help me. I tried to implement that using jquery hide and show.

You can use <asp:Button> controls for the other two buttons, and can set Visible="false" initially, then setting Visible="true" when you need to show them. This way, the server can do everything, and retain viewstate too so you don't have to reshow the buttons everytime the page posts back.
ASP buttons are standard buttons but can trigger the functionality you want through the OnClientClick property:
<asp:Button .. UseSubmitBehavior="false" Text="Move up" OnClientClick="moveSlider(1);return false;" />
<asp:Button .. UseSubmitBehavior="false" Text="Move down" OnClientClick="moveSlider(-1);return false;" />
Using return false; makes sure that the button doesn't postback, and UseSubmitbehavior="false" renders an <input type='button' /> instead.
HTH.

reset button is not working in asp.net

I have an asp.net web page that displays data that was returned from the database. However, when I attempt to click "Reset" (<input id="btnReset" type="reset" value="Clear" />) the button doesn't do anything.

The reset button will only erase the data the user entered after the page was rendered. So if you dont make any changes in the page, the reset button wont do anything.
Also, Reset is a client side operation. it wont post-back the page to the server.

you are probably looking for this
<asp:Button id="btnReset" Text="reset it!" runat="server" onclick="btnReset_onClick" />
so you can do stuff in your codebehind