Are you sure that is the GitHub Light theme? 

When I look at https://github.com/ryan-roemer/sphinx-bootstrap-theme/blob/master/sphinx_bootstrap_theme/__init__.py the website on the GitHub website looks different than your screenshot.

Textastic already includes a GitHub Light theme that looks similar to what I see on the linked GitHub website.

Here is a screenshot of that theme in Textastic:

Compare that to the GitHub website:

Messages and Facetime on Mac also use a similar style.

Hello,

I've downloaded your screenshot, zoomed in and looked at it. It looks find to me. There's a drop shadow behind the "T" and the "T" has a rounded appearance - but that's intentional, it's not blurry. Please compare this to the the Mac App Store icon which is very similar.

What did you try?

The important part is to make sure that your HTML and JS file is stored in the same folder somewhere in "Local Files", "iCloud" or in a folder added using "Add External Folder…". 

Also, make sure to use regular quotation marks for the src attribute:

<script src="script.js"><script>

I've answered your question in this topic: https://feedback.textasticapp.com/communities/1/topics/1333-linking-html-and-css-files

Hello,

make sure to store your HTML, CSS and JS files somewhere in "Local Files", "iCloud" or in a folder added using "Add External Folder…". 

You can link to your CSS file using a "link" tag in the HTML file's head section like this:

<link rel="stylesheet" href="example.css">

Similarly, you can link an external JavaScript file like this:

<script src="myscript.js"></script>

If you then preview the HTML file using the "glasses" icon, the CSS and JavaScript file should be loaded.

Please have a look at these topics in the manual for details:

https://www.textasticapp.com/v10/manual/managing_files/local_files_icloud.html

https://www.textasticapp.com/v10/manual/viewing_editing_files/web_preview.html

https://www.textasticapp.com/v10/manual/integration_other_apps/external_files_folders.html#adding-external-folders

Note: The web preview cannot load the referenced files if you opened a single HTML file from the Files app using Textastic's "Open…" command since that only gives Textastic access to the single file you selected and not to its containing folder.

Regarding the iCloud Documents folder: you can use the "Add External Folder" command to add the iCloud documents folder to Textastic. See https://www.textasticapp.com/v10/manual/integration_other_apps/external_files_folders.html

Textastic 10.4.1 ships with a new version of libcurl which fixes problems with uploading files to FTPS servers using TLS 1.3. The workaround to set the maximum TLS version to 1.2 is no longer necessary.

The problem was an improper shutdown of the TLS connection after the upload. As a result, the server rejected the uploaded data. See https://github.com/curl/curl/pull/13904 for details.