Educational Series 2015 , Create Email Account : Gmail
http://techtakyou.com/display-density-gmail-theme-inbox-styles/
Learn How To change Gmail Theme , Display Density And Inbox Styles
1 : "Display Density" settings

Gmail automatically adjusts the amount or “density” of information on a page when you adjust your browser window or when you use different sized screens (when you view your Gmail account on a small computer monitor versus a large one, for example). The “Display Density” setting affects how much space you see between labels, around inbox sections, and between individual messages in your inbox.

If you prefer a denser view no matter what size your monitor, then you can set a limit on your default density. This setting reflects the lowest density--the most space--permitted for your account. If you make your browser window smaller or move to a smaller screen, Gmail will still automatically resize to a higher density so that you can navigate your inbox with ease, but it will never be less dense than you requested.

2 : Gmail Theme

Personalize your Gmail by choosing a background theme, which adds some additional flair to your inbox.

Open Gmail.
Click the gear in the top right.
Select Themes.

Color, HD, and Classic themes --------------------------
Some themes change during the day, and if you select one of these themes, you'll see a drop-down menu to select a location. We'll use the location you provide to correctly time theme changes with your local sunrise, sunset, and/or weather. If you don't enter a city, or if you enter an invalid one, we'll set your location to the capital city of the country you selected.
You can tell which themes change by looking at the lower right hand corner of the theme's thumbnail image. Small icons indicate if the theme changes with the weather, time of day, or day of the week. Also, if you see a white corner it means that that the message list background in the theme is light; if it's black, that means it's dark.
Custom themes -------------------
Have a picture of your dog that you'd like to make your background theme? Have no fear, you can also select your own images to use as a theme. Select one of the two options under the "Custom themes" section: Light or Dark. You can then pick an image (we recommend that you select one larger than 2560 x 1920 px) from your computer, phone, photo albums, and the web.
You can also choose a custom theme from a selection of featured photos.

3 : Inbox styles and settings

Try out a new inbox style to quickly organize your inbox in a way that fits you best. Your inbox can be organized into tabs like Social and Promotions, or into sections like Unread, Starred, and Important.
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