searchmonkey, it's available from the repositories.
It's easy enough, but if you still need some help with it, ask me and I'll see if I can figure it out for you.
grep -R -i -a -n needle stack
grep is the tool needed to find text.
grep to search recursively.
grep to not be case-sensitive.
grep to treat binary files as plain text files.
grep to show you the line number where the needle is in the file.
needle is the piece of text you are looking for.
stack is where it should search. Because of the
-R parameter you can use a directory here.
grep -R -i -a -n "<html>" Websites
This will search for the text in every file in the folder Websites
I hope my explanation was enough for you to understand the use of all parameters. If not, feel free to ask more in a comment.