Video - Optimizing the Order of Scripts and Styles
This video by Tony Gentilcore, software engineer at Goggle, shows you two
easy-to-implement yet high-impact techniques for speeding up your web pages.
Most web browsers will serialize the download of script files, so we need to
to be careful about the order in which script files are included.
A script included before a CSS file may cause the browser to block. However,
simply moving the style above the script allows them to load in parallel.
So if you have an external script and an external CSS file, always include
the CSS file before the script, so that they will download in parallel.
Inline script tags, even though they don't download anthing, may prevent
subsequent resources from downloading in parallel with a CSS file. For
example if an inline script block is placed between an included style and
an included script, it serializes the downloads. If the inline script
block is moved above the style, parallelization is restored.
Watching for serialization points in the browser is an important technique
for speeding up your web page.