The Simple Measure of Gobbledygook (SMOG) formula from Harry McLaughlin can be used to calculate the reading level of copy that you have written. A SMOG calculator, and instructions for use, can be found on here: www.readabilityformulas. com/free-readability-formula-tests.php
Alternatively, www.flesh.sourceforge.net offers a Java application that produces the Flesch-Kincaid Grade Level and the Flesch Reading Ease Score of a document.
For an online dictionary and an online thesaurus, you can visit www.dictionary.com and www.thesaurus.com.
Read more about this in the Search engine optimisation chapter.
When it comes to keyword research there are a host of tools available. Have a look at the tools suggested in the chapter on SEO. Grammarly is a good one - www. grammarly.com.