SharePoint Modal Pop Up.

If you like the popup SharePoint Uses and wants to implement such in your code here is the code sample that can meet your requirements.

function OpenDocsDialog(url1) {
        var options = {
            url: url1,
            dialogReturnValueCallback: myDialogCallback
        };
        SP.UI.ModalDialog.showModalDialog(options);      
    }

    function myDialogCallback(dialogResult, data) {
        SP.UI.ModalDialog.RefreshPage(dialogResult)
    }

Here is how you can call the function :

function OpenPopup1() {
        OpenDocsDialog("URL");
        return false;
    }


If you want to implement it directly here is the sample code:
SP.UI.ModalDialog.showModalDialog({
    url: dialogUrl,        
    allowMaximize: true,        
    showClose: true,        
    width: 400,        
    height: 200,        
    title: "Pop Up",        
    dialogReturnValueCallback: RefreshOnDialogClose
});