Scrutiny has had a website spelling / grammar check since version 5.4.6. The enhancements below are available in version 5.8 which will be available shortly.
1. You'll need to make sure that spelling is enabled for this site (Settings screen). It slows the scan a little, so this setting is off by default.
2. Also choose the language that you want to check this site against. The languages you can choose from are the ones installed on your system (System Preferences > Keyboard > Text > Spelling > Set up)
3. Then kick the scan off for Spelling.
Protip: Note that the blue box is part of the app; if you're a keyboard rather than a mouse person, up and down arrows select the options on this screen. Return hits the Go button for the selected option, left and right arrow keys navigate previous and next through these screens.
4. When the results are ready, You'll now see two tabs. By page is the old view listing your pages with a count for spelling / grammar problems. The new tab is By word.
Note that there are some useful buttons just above the view.
5. You can now 'Learn' words (ie add them to your user dictionary) without entering the spelling dialog. In fact you can select as many words as you like in this view (hold cmd key to select non-contiguous items) and then add them all to your user dictionary by pressing 'Learn All Selected.
(Scrutiny uses the system user dictionary for the language you've chosen to check against. So it'll ignore any words you've already 'learned' using other applications.)
6. You can expand any word to see which pages it appears on. 'Expand all' and 'Collapse all' buttons are just above the view.
7. The spelling dialog is accessible from this view. Double-click a url or use the context menu after clicking a url. (Double-clicking a word won't work here because the dialog needs to know a page in order to show your word in context). The box shows the word in context (with next and previous buttons), suggested corrections. It has buttons for 'Learn' and 'Visit this page'.
9. The old and new views can be exported as html or csv.
The view that you are looking at will be exported, and in the case of the By word view, the exported file will reflect rows being expanded or collapsed. If you want to show everything, remember to 'expand all' before you export.