I'm a little confused on this topic mainly because I'm not quite sure how javascript loads in HTML. Currently, I have an "onload" method being called in the <body> tag. It calls a javascript function; checkBrowser() to check what kind of browser is being used. I normally have all my javascript library calls at the top of my HTML page as do I have my CSS file calls.

Where is my HTML page is the correct place to load Javascript & CSS files? Currently, the below script is at the bottom of my HTML page.

Code:
        function checkBrowser() {
            var navUserAgent = navigator.userAgent;
            var browserName = navigator.appName;
            var tempVersionOffset;

            HtmlLink css = new HtmlLink();

            css.Href = ResolveClientUrl("css/style.css");
            css.Attributes["rel"] = "stylesheet";
            css.Attributes["type"] = "text/css";
            css.Attributes["media"] = "all";

            if ((tempVersionOffset = navUserAgent.indexOf("Opera")) != -1) {
                browserName = "Opera";
                css.Href = ResolveClientUrl("css/StyleSheet.css");
            } else if ((tempVersionOffset = navUserAgent.indexOf("MSIE")) != -1) {
                browserName = "Microsoft Internet Explorer";
                css.Href = ResolveClientUrl("css/StyleSheet.css");
            } else if ((tempVersionOffset = navUserAgent.indexOf("Chrome")) != -1) {
                browserName = "Chrome";
                css.Href = ResolveClientUrl("css/chrome.css");
            } else if ((tempVersionOffset = navUserAgent.indexOf("Safari")) != -1) {
                browserName = "Safari";
                css.Href = ResolveClientUrl("css/safari.css");
            } else if ((tempVersionOffset = navUserAgent.indexOf("Firefox")) != -1) {
                browserName = "Firefox";
                css.Href = ResolveClientUrl("css/firefox.css");
            } else if ((tempVersionOffset = navUserAgent.indexOf("Edg")) != -1) {
                browserName = "Edge";
                css.Href = ResolveClientUrl("css/edge.css");
            }

            Page.Header.Controls.Add(css);

            css.Href = ResolveClientUrl("css/nav.css");
            Page.Header.Controls.Add(css);

            alert("BrowserName = " + browserName);
        }

Thanks,