Some individuals suggest that achieving a specific task without Flash is impossible, but I have personally witnessed it being accomplished using only HTML. This technique is often utilized in intricate demo and visualization applications as well as web applications.
The key lies in loading the page normally, followed by the activation of JavaScript code to preload all images and resources into a cache. Through JavaScript, one can monitor this process and display a progress bar to track its completion.
While the article primarily focuses on caching images, the first comment includes a link to an additional resource discussing caching other types of content:
This method is commonly employed when a webpage loads a significant portion of its content through AJAX requests. Implementing this approach would necessitate a structural adjustment to your website if you are not already utilizing AJAX for page loading. By using AJAX, you can initiate a request, display a spinner animation, and then implement an "ajax request complete" callback to remove the spinner and indicate completion. Although less interactive than a progress bar, this method still proves effective.
Alternatively, a simpler implementation involves adding a <div> immediately following the <body> tag to conceal the page contents. Upon triggering a jQuery ready event, the hidden <div> can be faded out to reveal the content. While lacking an interactive progress bar, this basic solution should suffice.