As a woman on a dating site currently, I can tell you that I get dozens of "you're beautiful" messages every day and I delete every one. Of course, you do want to choose a flattering picture to put up but I'm MUCH more interested in finding someone who matches my interests, education level, career path, etc. I am a person who wants to be treated with respect. The constant online "cat calls" have made me less open to online dating because it feels so much like the way I get harassed in real life. But it's hard to find new people any other way, so I just delete any messages about my appearance and focus on those who bother to read my profile and can write something intelligent and thoughtful. AFTER you have met someone in person and established a mutual connection, then you can compliment her appearance. But to do so in a first message on a dating site is a cat call and almost none of the women I know would respond well to that. Most of us automatically delete these.