Bravo Ivan. It's a nice and well-done template. As i can see you have changed the DOCTYPE of the site and you have done some other major changes.
Here is my 'negative' comments

- [No important] CSS Validation some errors have been generated. Take a look
here- [No important] HTML Validation some errors have been generated too. Take a look
here- [Important]
Specify a cache validator. The following resources are missing a cache validator. Resources that do not specify a cache validator cannot be refreshed efficiently. Specify a Last-Modified or ETag header to enable cache validation for the following resources:
http://fonts.googleapis.com/css?family=Armata&subset=latin,latin-ext http://fonts.googleapis.com/css?family=Lobster&subset=latin,latin-ext- [Important]
Defer parsing of JavaScript. 80.4KiB of JavaScript is parsed during initial page load. Defer parsing JavaScript to reduce blocking of page rendering.
http://www.itstudio.rs/templates/its/js/jquery-1.4.1.min.js (63.2KiB)
http://www.itstudio.rs/includes/js/elxis.js (10.4KiB)
http://www.itstudio.rs/administrator/includes/js/ajax_new.js (3.4KiB)
http://s7.addthis.com/js/250/addthis_widget.js (3.0KiB)
http://www.itstudio.rs/ (253B of inline JavaScript)
http://www.itstudio.rs/templates/its/js/custom.js (68B)
- [No so important]
Inline small JavaScript. The following external resources have small response bodies. Inlining the response in HTML can reduce blocking of page rendering.
http://www.itstudio.rs/ should inline the following small resources: http://www.itstudio.rs/templates/its/js/custom.js
- [Important]
Avoid CSS @import. The following external stylesheets were included in
http://www.itstudio.rs/templates/its/css/template_css.css using @import.
- [No so important]
Optimize the order of styles and scripts. The following external CSS files were included after an external JavaScript file in
http://www.itstudio.rs/. To ensure CSS files are downloaded in parallel, always include external CSS before external JavaScript.
http://www.itstudio.rs/templates/its/css/template_css.css http://fonts.googleapis.com/css?family=Armata&subset=latin,latin-ext http://fonts.googleapis.com/css?family=Lobster&subset=latin,latin-ext- [Important]
Specify image dimensions. The following image(s) are missing width and/or height attributes.
http://www.itstudio.rs/images/stories/Notepad-16b.png (Dimensions: 20 x 20) (2 uses)
http://www.itstudio.rs/images/stories/home.png (Dimensions: 32 x 32)
http://www.itstudio.rs/language/english/english.gif (Dimensions: 23 x 13)
http://www.itstudio.rs/language/serbian/serbian.gif (Dimensions: 23 x 13)
http://www.itstudio.rs/templates/its/images/logo.png (Dimensions: 179 x 100)
- [Important]
Optimize images. Some images can be optimized. There are:
Image source could save XX.Xkb (% of reduction that you can gain)
Losslessly compressing
http://www.itstudio.rs/templates/its/images/footer.png could save 11.3KiB (71% reduction).
Losslessly compressing
http://www.itstudio.rs/templates/its/images/header.png could save 8.3KiB (69% reduction).
Losslessly compressing
http://www.itstudio.rs/images/stories/home.png could save 2.8KiB (74% reduction).
Losslessly compressing
http://www.itstudio.rs/templates/its/images/hblur.png could save 2.7KiB (61% reduction).
Losslessly compressing
http://www.itstudio.rs/images/stories/bookmarks.png could save 2.7KiB (56% reduction).
Losslessly compressing
http://www.itstudio.rs/images/stories/Notepad-16b.png could save 2.6KiB (81% reduction).
Losslessly compressing
http://www.itstudio.rs/templates/its/images/logo.png could save 2.0KiB (18% reduction).
Losslessly compressing
http://www.itstudio.rs/images/stories/software/Inkscape.png could save 1.8KiB (46% reduction).
Losslessly compressing
http://www.itstudio.rs/images/stories/software/LibreOffice.png could save 510B (13% reduction).
Finally i don't like the red color at module CSS Sufix -sub
Particularity : file => layout.css line : 51
.moduletable-sub #active_menu {color:#aa2200;}
