Usually in a web page the <body> tag and <head> loads together in a webpage, Because of this often the webpage looks dull because sometimes the style sheets and java script load slowly and even several times it didn't load. So I am searching for a loader which will load the content which are in the head tag first and then after loading the content in the head tag then it will load the body content.
Is there such kind of script or any other trick to let the <head> tag load first
Pages load linearly from top to bottom. It will retrieve additional linked assets as it encounters them in the source. The order those assets are returned to the browser will depend on the path it takes and size of the files.
Your JS should not be linked from the HEAD section due to the fact that JS files can block concurrent loading of other assets. Instead, place your JS file links immediately before the </body> tag.
As for the CSS files, you COULD write a script that waits for the CSS to fully load before 'displaying' the rest of the page, but I'd strongly recommend AGAINST that, as this is simply how the internet works. The 'dull look' you are concerned about is really of no concern to anyone else that uses the internet.