By default vim treats two words connected with an underscore e.g. search_tag as a vim word text-object.
This is very useful because you can then use motions and commands on them such as daw to delete a word, or ciw to change inside the word.
That is not the case for dash separated words e.g. search-tag. These types of words are very common in CSS class names and HTML IDs.
To make vim treat dash separated words as a word text-object simply add the following to your .vimrc:
set iskeyword+=-And source it again.