TextEdit is a text editor that ships with Macs. As a program, it’s a simple and cheap web development tool. The only problem with it is that you will have to alter some of the Preferences to make it more user-friendly when developing web pages.
The following guide is a step-by-step tutorial for getting TextEdit ready to use as a web development tool.
Step One: Open TextEdit
Navigate to the Finder (the little smilely face in the Dock) and click Applications. Scroll down to ‘t’ for TextEdit.

Open TextEdit
Step Two: Select preferences
Select Preferences from the TextEdit menu, located in the upper-left hand corner of the menu bar.

Click on Preferences
Step 3: Select ‘Plain Text’
On the ‘New Document’ tab, make sure that ‘Plain text’ is selected, rather than ‘Rich text’

Select 'Plain text' in the New Document tab
Step 4: Change the opening and saving options
Click on the Open and Save tab. Under ‘When Opening a File:’ ensure that “Ignore rich text commands in HTML files’ is selected and that ‘Ignore rich text commands in rtf files’ is de-selected.
Under ‘When Saving a File:’ ensure that ‘Add “.txt” extension to plain text files’ is de-selected.

Step 5: Quit TextEdit
Almost there. To have the changes take effect, close the Preferences dialogue box and quit TextEdit by going to the TextEdit menu and selecting ‘Quit TextEdit’.

Quit TextEdit
Step 6: Re-start TextEdit
Re-start TextEdit and you are now ready to begin creating web pages. Just make sure that you add ‘.html’ (without the quotation marks) to your files.

TextEdit — ready to go