.htaccess (at least not in this case) - although it is because you are changing this URL-path (in
.htaccess) that you are experiencing this problem.
As @closetnoc suggested in comments, this problem is caused by using relative URLs in your HTML. Relative to what? Remember, it is the user-agent/browser that resolves relative URLs in your HTML, not the server. So, you need to fix your URLs; not
For example, if you are referencing your CSS file with a relative URL of the form
href="styles.css" (note, no slash prefix) and you are currently at the URL
example.com/view.php?id=15 then the browser will naturally resolve your CSS URL and request
example.com/styles.css (in the document root). However, if you are currently at the URL
example.com/watch/15 (effectively in a
/watch "subdirectory" [*1]) then the browser will resolve your relative CSS URL relative to a
/watch subdirectory, rather than the document root, so you end up with an absolute/resolved URL of the form
([*1] Note that "subdirectory" in this context is not necessarily a physical subdirectory on your server - it is a "subdirectory" in the URL-path; an additional path-segment. But the browser does not know the difference.)
The same applies if you are using relative URLs in your custom error documents (defined with the
ErrorDocument directive on Apache). The custom error document can potentially be called on any URL, so any relative URL to a static resource (CSS, image, JS, etc.) is going to be relative to the URL that caused the error, not relative to the error document itself (the location of which is effectively hidden from the user-agent).
Alternatively you can include a
base element in the
head section of your HTML document (although this is not without its caveats [*2]). This references the absolute URL that all relative URLs are relative to. In other words, since you are expecting these relative URLs to be relative to the document root then add the following to the
Now, a relative URL such as
styles.css referenced in a document at URL
/watch/15 will request
[*2] There are, however, some caveats with using the
base element. A primary concern is that any relative URL that is intended to target the current document will now target the base URL instead. This can effect in-page anchors like
href="#top" and URLs of the form
href="?sortby=date" etc. And also
form elements that submit to themselves using an empty
action attribute (eg.
<form action="" ...). These relative URLs that target the current document will need to be modified to include the full URL of the current page (which may defeat the point of using the
base tag as a workaround to begin with).