Some of the web pages that I need to be open, while developing my script, produce a lot of errors that go into the Error Console of the Firefox. This makes it really hard to spot the errors, which are produced by the script, that I am trying to develop. Is there any way to filter the errors in Error Console? For example display only those that begin with my custom tag.
Sounds like you need a console prividing some filter and search capabilities like Console². It replaces the standard console with a more powerful version and works quite well. And it has a search box.