For those attributes that can stretch into infinity and beyond off-screen and do not tolerate white space like urls.
Without knowing exactly what your question refers to, it's hard to say; but it's worth pointing out that html is more or less insensitive to white-space, so
<img src="path/to/image.png" height="200px" width="400px" class="title" id="mainTitle" onClick="alert('clicked')" style="display: block; float: right; position: relative;" />
is equivalent to
<img
src="path/to/image.png"
height="200px"
width="400px"
class="title"
id="mainTitle"
onClick="alert('clicked')"
style="display: block; float: right; position: relative;" />
I'm not wholly certain that it's possible, or valid, to separate the attribute/value pairs across lines, but certainly each pairing can be separated from the next/previous pair.
Incidentally, even Notepad allows for line-wrapping (under 'edit' or 'view', I'm not sure which since I switched to Linux full-time a few years back).