I wish to take away the label "Search" in Joomla search module (default search module). I've modified the default_form.php in the directory /joomla15/components/com_search/sights/search/tmpl/ as well as removed the next code however it does not matter on the website:

    <label for="search_searchword">
    <?php echo JText::_( 'Search Keyword' ); ?>:
</label>

Really i'm utilizing an image button for that Search and that i dont want the label to become displayed. What must i do in order to take it off?

You should not be hacking Joomla Core Files. If you wish to change a view from the component, you need to use Template Overrides.

Second, if you are modifying your research component, you should know the extensions in Joomla are divided in "Components", "Plug ins" and "Modules". Every module is definitely an extension, although not every extension is really a module. It's quite different using their company CMS's you might be accustomed to.

This is exactly why you cannot improve your search "module". You are trying to find it's templates in components folder when you be considering "modules" folder too.

There is a search module, that seems in most pages. This module is within JOOMA_PATH/modules/mod_search/tmpl/default.php, and you ought to be copying it to JOOMA_PATH/templates/TEMPLATE_NAME/html/mod_search/default.php to include your modifications. This really is way, when upgrading your Joomla installation, you are not likely to lose your custom remaking.

I not used at all Joomla! and so i just guess but maybe there's some type of template cache? Attempt to obvious it.

But what you are attempting to do is an extremely bad practice. This label makes your forms more available (for screen visitors etc.). Create remove this element - just hide it using CSS:

#mySearchForm label {
    display: none;
}