Put the summary of the bug you're having here

I hit Play and it goes to the page that says Mojang and then crashes.
Then this kind of message appears:

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 1/25/14 4:26 PM
Description: Registering texture

java.lang.OutOfMemoryError: Java heap space
at java.awt.image.DataBufferByte.<init>(Unknown Source)
at java.awt.image.ComponentSampleModel.createDataBuffer(Unknown Source)
at java.awt.image.Raster.createWritableRaster(Unknown Source)
at javax.imageio.ImageTypeSpecifier.createBufferedImage(Unknown Source)
at javax.imageio.ImageReader.getDestination(Unknown Source)
at com.sun.imageio.plugins.png.PNGImageReader.readImage(Unknown Source)
at com.sun.imageio.plugins.png.PNGImageReader.read(Unknown Source)
at javax.imageio.ImageIO.read(Unknown Source)
at javax.imageio.ImageIO.read(Unknown Source)
at bqs.b(SourceFile:112)
at bqs.a(SourceFile:90)
at bqy.a(SourceFile:72)
at bqy.a(SourceFile:61)
at bqy.a(SourceFile:52)
at azi.ad(SourceFile:422)
at azi.f(SourceFile:696)
at net.minecraft.client.main.Main.main(SourceFile:152)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at java.awt.image.DataBufferByte.<init>(Unknown Source)
at java.awt.image.ComponentSampleModel.createDataBuffer(Unknown Source)
at java.awt.image.Raster.createWritableRaster(Unknown Source)
at javax.imageio.ImageTypeSpecifier.createBufferedImage(Unknown Source)
at javax.imageio.ImageReader.getDestination(Unknown Source)
at com.sun.imageio.plugins.png.PNGImageReader.readImage(Unknown Source)
at com.sun.imageio.plugins.png.PNGImageReader.read(Unknown Source)
at javax.imageio.ImageIO.read(Unknown Source)
at javax.imageio.ImageIO.read(Unknown Source)
at bqs.b(SourceFile:112)
at bqs.a(SourceFile:90)

– Resource location being registered –
Details:
Resource location: minecraft:textures/atlas/blocks.png
Texture object class: bqs
Stacktrace:
at bqy.a(SourceFile:72)
at bqy.a(SourceFile:61)
at bqy.a(SourceFile:52)
at azi.ad(SourceFile:422)

– Initialization –
Details:
Stacktrace:
at azi.f(SourceFile:696)
at net.minecraft.client.main.Main.main(SourceFile:152)

– System Details –
Details:
Minecraft Version: 1.7.4
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 18500576 bytes (17 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.7.4
LWJGL: 2.9.1
OpenGL: Intel(R) HD Graphics 3000 GL version 3.1.0 - Build 9.17.10.2843, Intel
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: [Davids Detailed 64x64.zip, Sphax PureBDcraft 512x MC17.zip]
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~_ERROR~ NullPointerException: null
Anisotropic Filtering: Off (1)