website design - Which label text is good for "Enter email address"?

I'm about to place one text field in the log in area where user can enter email address and password for logging in, but I'm confused which text should I use for label and placeholder text?

Here are some examples where I found some different ideas.

Gmail:

• Only placeholder with text "Email"

Yahoo Mail:

• Only placeholder with text "Yahoo ID"

Outlook.com:

• Only placeholder with text "someone@example.com"

Which one should I use? Only placeholder, or with label?

Also, a couple more question. If I use label, should the text and placeholder be "Email", "Email address" or "Enter Your Email", "Enter Your email address"?

Which one is better? "E-mail" or "Email"? Logically E-mail is the right one but somewhere I've also seen "Email" in place of "E-mail".

Answer

I wouldn't use only a placeholder because of the browser support. Not all old browsers support the placeholder! Take a look to this Stackoverflow Question and to this article about placeholder support.

And I wouldn't use the term "Email ID". Many users are confused about the "ID". I also heard many stories about the confusion of the "Yahoo ID".
"Should I insert here an email or a username? Do I have a username on Yahoo?"
Just use "E-Mail". It is simple and clear for all users.

So for me the best practice is to use a label with "E-Mail" and a placeholder with an example Mail:

E-Mail">

Edit
I found an interesting article about your question "Email or E-Mail".
It say that official you should use Email.

A group calling itself the Email Experience Council has declared the official term to be email.

But many famous companys (e.g Microsoft) use also E-Mail. And in my opinion, E-Mail looks even better for me.
But keep your own counse and take a look to the article by The Fiction Desk.

Edit 2
I think I found the mistery of E-Mail / email!
On the english wikipedia, there is a really interesting part about the spelling:

e-mail is the most common form in print, and is recommended by some prominent journalistic and technical style guides. According to Corpus of Contemporary American English data, this is the form that appears most frequently in edited, published American English and British English writing.

email is the most common form used online, and is required by IETF Requests for Comment and working groups and increasingly by style guides. This spelling also appears in most dictionaries.

mail was the form used in the original RFC. The service is referred to as mail and a single piece of electronic mail is called a message. eMail, capitalizing only the letter M, was common among ARPANET users and the early developers of Unix, CMS, AppleLink, eWorld, AOL, GEnie, and Hotmail.

EMail is a traditional form that has been used in RFCs for the "Author's Address", and is expressly required "for historical reasons".

E-mail is sometimes used, capitalizing the initial letter E as in similar abbreviations like E-piano, E-guitar, A-bomb, H-bomb, and C-section.

Source en.wikipedia

And the reason why I like "E-Mail" the most is, that i'm from Switzerland, where I speak German. And in the German Dictionary, there is "E-Mail" the official version.
Source de.wikipedia