Code:

.ui-widget-overlay{
    position:fixed;
}

Code:

// Prevent jQuery UI dialog from blocking focusin
$(document).on('focusin', function(e) {
    if ($(event.target).closest(".mce-window").length) {
        e.stopImmediatePropagation();
    }
});

Code:
namespace MuzickaProdavnica.EF
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.Web.Mvc;
    
    public partial class Obavestenja
    {
        public int Id { get; set; }
        public Nullable<System.DateTime> DatumObjave { get; set; }
         [Required(ErrorMessage = "!")]
        public string Naslov { get; set; }
        [Required(ErrorMessage = "!")]
        [UIHint("tinymce_jquery_full"), AllowHtml]
        public string Tekst { get; set; }
        public string PutanjaDoFajla { get; set; }
        public string Korisnik { get; set; }
        public Nullable<int> Aktivan { get; set; }
    }
}

Code:
@model MuzickaProdavnica.EF.Obavestenja

@{
    ViewBag.Title = "Test1111";
    //Layout = "~/Views/Shared/_Layout.cshtml";
}

@Html.ValidationSummary(true, "Neuspešan unos obaveštenja!")

 <div id="unos_obavestenja" style="display: none">

@using (Html.BeginForm("Unos", "Obavestenja", FormMethod.Post, new { id = "upisi", enctype = "multipart/form-data" }))
{
   
        <fieldset id="fildset_unos">
            <legend>Novo obaveštenje test</legend>

            <div class="editor-label">
                @Html.LabelFor(m => m.Naslov)
            </div>

             @Html.AntiForgeryToken()
            <div class="editor-field">
                @Html.TextBoxFor(m => m.Naslov )
                @Html.ValidationMessageFor(m => m.Naslov)
            </div>

             @Html.AntiForgeryToken()
            <div class="editor-label">
                @Html.LabelFor(m => m.Tekst)
            </div>
            <div class="editor-field-text_unos">
                @Html.EditorFor(model => model.Tekst,new { style = "width:800px; height: 300px; " })
                @Html.ValidationMessageFor(m => m.Tekst)
            </div>

             <label for="file">Datoteka:</label>
             <input type="file" name="fajl"  />        
            
        </fieldset>    

}

     </div>


<script type="text/javascript">
    
    $(document).on('focusin', function (e) {
        if ($(event.target).closest(".mce-window").length) {
            e.stopImmediatePropagation();
        }
    });


</script>

Code:
$('#EditBtn').live('click', function () {
                
        $("#unos_obavestenja").dialog({            
            
            width: 800,                            
            modal: true ,
            buttons: {
                "Upiši obaveštenje": function () {
                    $("#upisi").submit();
                   
                    return true;
                },
                "Odustani": function () {
                    $(this).dialog("close");
                }
            },       
        
        
        });      
        
    });