Here are some tips for saving sharp imagery in Photoshop
1.When you are working with text, select "Crisp" or "Sharp" from the Character window.
Character window is at the very top menu option: Window -> Character.
2. Rasterizing converts images into pixels that can be displayed on screen.
You can rasterize the text which will create outlines around the letters. This way Photoshop renders it as any other image on your document.
Right click on your text layer and select Rasterize Text
3. This is the main step for optimizing.
From the top menu, select File > Save for Web (might be called Save for Web and Devices).
This will open a window with a bunch of options. For best results, select these presets: JPEG High, JPEG, Maximum. and hit Save